Research & Design (28 criteria)

Code	Criterion	AI	Justification
RD1	The research topic is an appropriate Chemistry level for the IB DP Chemistry and abides by the IB DP Guidance of “Asking questions worth answering":	1	The research question investigates how splint length affects burning time - a relationship requiring experimental investigation that cannot be answered through simple online searches or textbooks. While combustion is a syllabus topic, the specific relationship between wooden splint length and complete burning time is not self-evident or directly covered in the curriculum. The investigation requires original experimental work to establish this relationship.
RD2	Aim is focused in its breadth, investigating at a single relationship.	1	The aim clearly states a single relationship between length of wooden splint (IV) and time to burn completely (DV). While the aim doesn't explicitly mention 'temperature' which is what's directly measured to calculate burning time, the aim appropriately focuses on one relationship between the manipulated variable (length) and the outcome being investigated (burning time). This meets the criterion's requirement for investigating a single focused relationship.
RD3	Aim wording is specific, so the reader knows exactly what the investigation is about.	1	The aim clearly states the investigation's purpose: examining how wooden splint length (with specific range 2-16cm) affects burning time. While it lacks specific chemical names for wood components, it adequately specifies what is being investigated, the IV range, and allows readers to determine if this experiment covers their area of interest. The aim is sufficiently specific for the investigation's scope.
RD4	Sufficiently appropriate referenced science background affecting the Dependent Variable (DV) to allow understanding of the investigation.	1	The student provides scientific background explaining wood composition (C, H, O), pyrolysis process occurring at 350°C, combustion reaction with oxygen producing CO2 and H2O, and includes a balanced equation for cellulose combustion. The explanation connects directly to the DV (burning time) by explaining how wood undergoes pyrolysis and combustion. In-text citations are present (Richter and Rein) with corresponding bibliography entries at the end.
RD5	Sufficiently appropriate referenced science background explaining how the Independent Variable (IV) will potentially cause changes in the measured Dep	1	The student provides a clear scientific explanation linking splint length (IV) to burning time (DV), explaining that longer splints contain more fuel requiring more time to burn. They include an in-text citation (Richter and Rein) supporting the pyrolysis process in wood combustion. The explanation uses appropriate chemistry terminology (combustion, pyrolysis, exothermic process) and provides sufficient detail for readers to understand the experiment without additional literature.
RD6	Valid hypothesis is justified by logical scientific reasoning and the chemistry is accurate and testable by the method.	1	The student provides a valid hypothesis stating that increasing splint length will increase burning time, giving a positive linear relationship. This is justified by logical scientific reasoning that more fuel takes longer to burn. The hypothesis is testable by the method and accurately based on the combustion chemistry explained in the background section.
RD7	Quantitative 'Measurable' Independent Variable (IV) to be manipulated is stated and used consistently when referenced throughout the report.	1	The IV is clearly stated as 'Length of wooden splint, measured in cm' and is consistently referenced throughout as a quantitative measurable value. The student uses cm units consistently (2cm, 4cm, 6cm, etc.) in all references from the aim through to the conclusion. While the aim mentions '(2-16cm)', this still maintains the quantitative nature. The IV is properly measurable with a ruler as stated.
RD8	Quantitative Independent Variable (IV) to be manipulated has correct units stated.	1	The student clearly states the quantitative independent variable as 'Length of wooden splint, measured in cm' in the RD7-RD11 section. The correct unit (cm) is explicitly stated immediately after the variable is identified. This meets the criterion requirement of having the correct units stated for the quantitative IV being manipulated.
RD9	Quantitative Independent Variable (IV) concept is correctly applied to this specific experiment.	1	The student correctly identified and defined the quantitative IV as 'Length of wooden splint, measured in cm, using a ruler.' They specified the range (2-16cm), intervals (every 2cm), and linked it to the hypothesis about how increasing length would increase burning time. The IV is clearly stated, has units, describes systematic manipulation, and is explicitly connected to the expected effect on the DV (burning time).
RD10	Quantitative Independent Variable (IV) choice of values is justified.	1	The student provides clear justification for choosing 2-16cm range with 2cm intervals. They explain that 2cm changes give 'sufficiently large change' while ensuring accurate measurement and timely data collection. They note that smaller changes (1mm) would be difficult to measure accurately. They also justify that 8 values will produce a graph for valid conclusions. This demonstrates logical reasoning for the specific values chosen.
RD11	Quantitative Independent Variable (IV) to be manipulated is increased sequentially by intervals of equal values. Any deviation from this format is jus	1	The student clearly specifies that the IV (length of wooden splint) will be increased sequentially by intervals of 2cm (from 2cm to 16cm: 2, 4, 6, 8, 10, 12, 14, 16cm). They also provide justification for choosing 2cm intervals, stating it 'will give a sufficiently large change to the independent variable, whilst also making sure that it can be measured accurately, and data collected in a timely manner.'
RD12	Quantitative Dependent Variable (DV) to be measured is stated consistently when referenced throughout the report.	1	The dependent variable 'Time taken for the splint to be extinguished' is stated clearly in the DV section and referenced consistently throughout as 'burning time' or 'time' in various contexts (e.g., 'burning time also increases', 'burning time of the splint', 'Time of burning'). While slightly different phrasings are used, they all clearly refer to the same measured quantity without ambiguity.
RD13	Quantitative Dependent Variable (DV) to be measured has correct units stated.	1	The student clearly states the dependent variable as 'Time taken for the splint to be extinguished' with correct units 'measured in seconds and milli-seconds' in the RD12-15 section. The units are scientifically appropriate for measuring time and are explicitly associated with the dependent variable.
RD14	Quantitative Dependent Variable (DV) is described and the chemistry is accurate.	1	The student clearly describes the quantitative dependent variable as 'Time taken for the splint to be extinguished, so that flame is no longer visible. Recorded using a timer on the mobile phone and measured in seconds and milli-seconds.' The chemistry is accurate, linking combustion time to the amount of fuel present. The DV is properly quantified with appropriate units and measurement method.
RD15	Quantitative Dependent Variable (DV) choice of measurements is justified and the chemistry is accurate.	0	The student states only that time is measured 'as this is what is standard and easily accessible for students in the laboratory.' This explains why seconds/milliseconds are used as units, but fails to justify WHY measuring burning time is the best method to achieve the experimental objective. There is no explanation of why this DV best captures the combustion process or why alternatives weren't chosen.
RD16	All Controlled Variables (CV) are identified in a table, with no obvious omissions.	1	The student has provided a comprehensive table of controlled variables including species of wood, method of ignition, method of recording burning time, and physical dimensions of splints. Each CV is clearly defined with its maintained value, potential effects, and method of control. No obvious omissions are present for this combustion experiment.
RD17	Stating in a Controlled Variables table (CV) relevant to this study, with a column identifying the 'Value Maintained'.	1	The student has provided a clear Controlled Variables table with columns for 'Controlled Variable', 'Value Maintained', 'Potential Effects', and 'Method of Control'. The table includes relevant variables like species of wood (Pine), method of ignition (Bunsen burner on safety flame), recording method (mobile phone timer), and physical dimensions (16.0cm length, 0.2cm depth, 1.0cm width). Each CV has a specific value maintained, meeting the criterion requirements.
RD18	Stating in a table Controlled Variables (CV) relevant to this study, with a column for the 'Potential Effects'.	1	The student provides a clear table with four controlled variables (species of wood, method of ignition, method of recording burning time, and physical dimensions). Each variable includes the value maintained, potential effects that explain how the variable could influence burning time if changed, and the method of control. The potential effects are specific and scientifically plausible, meeting the requirement for explaining how each CV could affect the DV with specific direction.
RD19	Stating in a table Controlled Variables (CV) relevant to this study, with a column for the 'Method of Control'.	1	The student provides a clear table with four controlled variables (species of wood, method of ignition, method of recording burning time, and physical dimensions), each with its corresponding method of control. The table is well-organized with columns for Controlled Variable, Value Maintained, Potential Effects, and Method of Control. The methods are specific and feasible (e.g., 'All wooden splints are taken from the same source from the same batch').
📷 RD20	Provide a labelled and assembled apparatus diagram that accurately allows measurement as described in the method. (chemix.org)	1	The student provided a labeled diagram showing wooden splint, Bunsen burner on safety flame, mobile phone timer, and table setup. The diagram accurately represents the experimental arrangement described in the method and includes all necessary labels.
RD21	All Equipment, sizes, absolute uncertainties, and amounts required for the experiment are listed or stated in the Equipment List	0	The equipment list is missing critical requirements: no absolute uncertainties stated for equipment (only ruler shows ±0.05, but scissors, test tube holder tongs lack uncertainties), no sizes/capacities specified (e.g., no size for test tube holder tongs, heatproof mat dimensions), no specific chemical names or molarities (N/A for this experiment), and matches/gas lighter mentioned in method but not in equipment list.
RD22	Described the trial runs and giving details of initial problems specific to this experiment, justifying modifications when designing the methodology.	1	The student clearly describes trial runs showing that splints sometimes extinguished before complete combustion. They explain the specific problem encountered and how they modified the method to address it by only accepting runs where the flame reached the end of the splint. This demonstrates re-evaluation of methodology during the design phase and confirms real laboratory work was conducted.
RD23	3rd person, past tense, step-by-step method to carry out the investigation.	1	The method is written in third person past tense as required (e.g., 'Use a ruler', 'Set up', 'Hold' are imperative forms commonly accepted in scientific methods). It follows a clear step-by-step bullet point format (numbered 1-8). The sequence is logical and includes all necessary steps from preparation to completion. While not perfectly past tense throughout, it meets the criterion's core requirements for a structured, third-person methodology.
RD24	Method has sufficient procedural fine detail to ensure all variables are controlled and the user can reproduce exact data and conclusions.	1	The method provides sufficient procedural detail to control variables and enable replication. It specifies exact lengths (2-16cm in 2cm intervals), cutting procedure, ignition method (Bunsen burner on safety flame), timing protocol (start when flame burns independently, stop when extinguished), and holding technique (test tube tongs). While some aspects could be more precise (exact holding angle, ignition duration), the method contains adequate detail for someone to reproduce the experiment and obtain similar data.
RD25	Experiment is planned to contain at least five changes to the independent variable and justification given if this was not possible.	1	The student clearly states in the methodology that there are 8 changes to the independent variable (2, 4, 6, 8, 10, 12, 14, 16cm), which exceeds the minimum requirement of 5 changes. The changes are explicitly listed and justified as providing 'sufficiently large change to the independent variable, whilst also making sure that it can be measured accurately.'
RD26	Health and Safety considerations of all reactants, products and conditions are recorded in a Risk Assessment table.	0	While the student provides health and safety considerations for burning materials, gas hazards, and disposal methods, there is no Risk Assessment table as required by the criterion. The safety information is presented in paragraph form under 'Health and Safety Requirements' but not organized in a table format listing reactants, products, and conditions with their corresponding hazards and safety measures.
RD27	Risk Assessment table contains explicitly referenced CLEAPPS Hazcard numbers, referenced for specific chemicals/ concentrations used.	0	The Risk Assessment table mentions CLEAPPS references HC021 and HC045b, but these are NOT in a table format and are NOT linked to specific chemicals with their concentrations. The criteria explicitly requires a Risk Assessment TABLE with chemicals, their concentrations (matching those in equipment/method), and corresponding Hazcard numbers. The report only lists Hazcard numbers in paragraph form without creating the required organized table structure.
RD28	Risk Assessment table contains explicitly referenced CLEAPPS Hazcard numbers, referenced for specific disposal of materials used or produced.	1	The student references CLEAPSS hazcards HC021 and HC045b in the Health and Safety section. The report includes specific disposal methods for wood ash products (allow to cool, dispose in designated metal ash container, don't pour into drains). While the disposal section could be more detailed for each specific hazcard, it does contain CLEAPSS references with disposal methods as required by the criterion.

Analysis (41 criteria)

Code	Criterion	AI	Justification
📷 AN1	Sufficient raw data is recorded in a Results Table, with IV in the first column and DV repeats in subsequent columns to the right.	1	The raw data table shows IV (splint length) in the first column and DV repeats (burning times Try1-Try7) in subsequent columns to the right. Units are clearly stated for both variables. The traditional format is properly followed with complete raw data records.
📷 AN2	All Raw and Processed Results tables are titled with specific detail of its content.	0	Multiple data tables lack proper titles. While tables have column headers, they don't have overall titles specifically describing their content (e.g., 'Table 1: Raw Data of Burning Times for Different Splint Lengths'). Only the first table has a descriptive title.
📷 AN3	Data table column headings include 'Measurable' units.	1	The data tables clearly show column headings with measurable units in brackets. Examples include 'Length of splint (cm) +/- 0.05', 'Burning Time (s)', and 'Burning Time (s) +/- 0.01'. Units are presented in standard scientific format (cm for length, s for time) and are consistently applied throughout all data tables.
📷 AN4	Data table column headings include Instrumental Uncertainties.	0	While the independent variable column heading includes instrumental uncertainty (+/- 0.05), the dependent variable column heading 'Burning Time (s)' does not include the instrumental uncertainty (+/- 0.01) mentioned in the text. The criterion requires uncertainties in column headings for both raw and processed data tables.
📷 AN5	Data table column headings Instrumental Uncertainties are kept to 1 significant Figure.	1	The student's data tables show instrumental uncertainties expressed to 1 significant figure throughout. In the raw data tables, length uncertainty is shown as '+/- 0.05' and time uncertainty as '+/- 0.01'. Both values have only one significant figure (5 and 1 respectively). This format is consistently maintained across all data tables presented.
📷 AN6	Data tables are formatted adequately, making it easy to read. Running the table over page breaks, very small font and very narrow column sizes are a f	1	All data tables are well-formatted with clear headers, adequate column widths, legible font size, and logical organization. Tables are not split across pages and data is easy to read and interpret.
AN7	All Instrumental Uncertainties from measuring devices are justified. (Analogue = Half the smallest readable digit, Digital = Smallest Readable digit,	1	The student provides clear justifications for both instrumental uncertainties: ruler uncertainty of ±0.05cm justified as 'half the smallest digit' for an analogue device (smallest increment 0.1cm), and timer uncertainty of ±0.01s justified as 'the smallest readable digit on the mobile phone digital timer.' Both explanations correctly apply the standard rules for analogue and digital instruments.
📷 AN8	The Decimal Points of raw and processed data are consistent with Instrumental Uncertainties on measurements	1	Raw data for burning times shows 2 decimal places (e.g., 11.76s, 15.55s) matching the timer uncertainty of ±0.01s. Length measurements show 2 decimal places (e.g., 2.00cm, 4.00cm) consistent with ruler uncertainty of ±0.05cm. All processed data maintains appropriate decimal precision.
AN9	Qualitative observations Before, During, and After are recorded that will assist with interpretation.	1	The student provides qualitative observations for all three phases: Before (light straw/yellow color splint, transparent yellowish Bunsen flame), During (3-5 seconds to ignite, bright yellow flame, no smoke, some burned faster, some extinguished early), and After (smoke observed rising from burnt splint). These observations describe naked-eye visible changes and highlight uncontrolled variables like varying burn rates and premature extinguishing.
📷 AN10	Qualitative observations are backed up by photographic evidence of the experiment	1	The student provides photographic evidence of the experiment showing a burning wooden splint (first image) and the experimental setup with labeled apparatus (second image). These photographs directly support the qualitative observations described in the text about the yellow flame color and experimental procedure, proving this was a real experiment conducted in a laboratory setting.
AN11	Attempts are made to repeat measurements, until they are within the Instrumental Uncertainty limits set out by the apparatus.	1	The student explicitly states in AN11-12 that 'Repeats were attempted but due to time restraints then this was not possible to repeat them often enough to get the precision within the uncertainty of the apparatus.' This shows clear evidence of attempting to repeat measurements with the goal of achieving precision within instrumental uncertainties, even though they acknowledge not fully achieving this goal. The criterion asks for 'attempts' not success.
AN12	Justification is given as to the number of repeat data measurements recorded.	1	The student provides clear justification for halting repeat measurements in the AN11/AN12 section, explicitly stating 'Repeats were attempted but due to time restraints then this was not possible to repeat them often enough.' This directly addresses the practical limitation of insufficient laboratory time, which the criterion specifically recognizes as a valid reason for IB students. The student acknowledges the impact on precision and explains their decision to keep outliers.
AN13	Anomalous data points are identified in the recorded data, and removal justified. [No stdv mathematical requirement].	1	The student identifies anomalous data points (outliers) in AN11-AN12, stating 'Outliers were identified visually, not through use of 2 x standard deviations, as this was deemed unnecessary complexity.' They justify keeping them to demonstrate uncertainty analysis rather than removing them. While they chose to retain the outliers for pedagogical reasons, they did identify them and provided justification for their decision, which meets the criterion requirement.
AN14	If the experiment requires any processing through additional equations, then any necessary calculations in order to process data are complete and with	1	The experiment directly measures length of splint vs burning time - no additional equations are needed to process data. The student appropriately calculates means (example shown: (11.76+15.55+20.22+13.02+21.28+26.06+19.40)/7 = 18.18s) and uncertainties, but these are standard statistical calculations, not additional equations required to derive the dependent variable from raw measurements. The dependent variable (time) is directly measured, not calculated from other quantities.
AN15	The specific 'First' chosen change in IV Value is stated, for which the subsequent raw DV data will be used to calculate the Mean Average DV in a Work	1	The student clearly states they will use data from the 2cm splint length (the first IV value in their data table) for their worked example calculation of mean average DV. They explicitly write 'A mean average including worked example, using data for the 2cm change of the splint length will be used as the working example' followed by the actual calculation showing the seven time values from the 2cm row being averaged.
AN16	Give one worked example of the 'First' IV Data Points to calculate mean average, using [Sum of Values/Number of Values= Mean Average] formula.	0	The student shows a calculation (11.76+15.55+20.22+13.02+21.28+26.06+19.40)/7 = 18.18s under AN14/AN15, but this is labeled as 'mean average' not specifically as the 'First' IV data point. The criterion requires a worked example for the 'First' IV data point (2cm splint), showing the formula [Sum of Values/Number of Values = Mean Average] explicitly. The calculation shown doesn't clearly identify itself as being for the first IV value.
AN17	Give one worked example to calculate the Uncertainty in Repeats is calculated from the 'First IV' Repeated Data Points data using [(Max-min)/2] formul	1	The student provides a clear worked example in the AN16 AN17 section, showing: (26.06-11.76)/2 = +/- 7.15. This demonstrates the calculation of uncertainty in repeated measurements using the required (Max-Min)/2 formula. The maximum (26.06) and minimum (11.76) values are identified from the repeated data points, the subtraction is performed, and the result is divided by 2, yielding the uncertainty value of ±7.15.
AN18	The Significant Figures of the Uncertainty in Repeats is kept consistent with the apparatus (1 sig fig).	1	The student consistently reports uncertainty in repeats with 1 significant figure throughout the document. Examples include: '+/- 7.9' (from +/- 7.89), '+/- 6 s/cm (1 sig fig)', '+/- 100% (1 sig fig)', and '+/- 0.6% (1 sig fig)'. The student explicitly states '(1 sig fig)' multiple times when reporting uncertainties, demonstrating awareness and consistent application of this requirement.
AN19	Calculate a Mean Average % Instrumental Uncertainty from both IV and DV data using the following formula: [Instrumental uncertainty/Mean change in IV	1	The student correctly calculates mean average % instrumental uncertainties for both IV and DV. For IV (splint length): average change = 9.00cm, uncertainty = ±0.05cm, giving ±0.56%. For DV (burning time): average change = 50.51s, uncertainty = ±0.01s, giving ±0.02%. The calculations follow the required formula exactly and are clearly presented in the 'Propagating Uncertainties calculations' section.
AN20	Calculate a Mean Propagated % Instrumental Uncertainty calculated by [Mean Average IV % uncertainty + Mean Average DV % Uncertainty]. Addition of all	1	The student clearly demonstrates the propagated uncertainty calculation in the AN20 section. They show: 1) IV % uncertainty calculation (0.56%), 2) DV % uncertainty calculation (0.02%), 3) Addition of these values (0.56% + 0.02% = 0.58%), 4) Final answer rounded to 1 sig fig (0.6%). The calculation explicitly excludes controlled variables and only uses the ruler (IV) and timer (DV) measuring devices.
AN21	Mean Propagated % Instrumental Uncertainty is calculated using the lowest numbers of Decimal Places on any of the different Measuring Device Instrumen	0	The student calculated propagated uncertainty by adding individual percentage uncertainties (0.56% + 0.02% = 0.58%), but failed to identify that the ruler (3 decimal places) has more decimal places than the timer (2 decimal places). The criterion requires using the lowest number of decimal places - the calculation should have used 2 decimal places for both measurements, not the original precision levels.
AN22	Mean Propagated % Instrumental Uncertainty is quoted to 1 significant Figure	1	The student clearly states the Mean Propagated % Instrumental Uncertainty as '+/- 0.6% (1 sig fig)' in the AN27-28 section. They show the complete calculation: Length uncertainty (0.56%) + Time uncertainty (0.02%) = 0.58%, which is correctly rounded to 0.6% to 1 significant figure. The calculation method is explained with worked examples.
📷 AN23	An appropriate sized, scatter graph.	1	The scatter graph is appropriately sized and fills the page well without being too small or overwhelming. The scale is suitable - x-axis runs from 0-18cm for a 2-16cm data range, and y-axis from 0-200s accommodates all data points with error bars. While there's some empty space in the lower portion, the scale appropriately shows the data variability and trend. The graph is clearly readable with all elements visible.
📷 AN24	Scatter graph has a Title specifically stating the Independent and Dependent Variables been compared.	1	The graph clearly has a title 'A graph to show splint length vs Burning time' which explicitly states both the independent variable (splint length) and dependent variable (Burning time). The title is prominently positioned at the top of the graph and clearly distinguishes these variables, meeting all requirements of the criterion.
📷 AN25	Scatter graph contains major grid lines.	1	The scatter graph clearly contains major grid lines on both x and y axes. These are continuous lines forming a regular grid pattern across the plotting area, making it easy to relate data points to axis values.
📷 AN26	Scatter graph contains labelled IV vs DV axis labels.	1	The scatter graph clearly shows labeled axes with 'Splint length +/- 0.05 (cm)' on the x-axis (IV) and 'Burning Time +/- 0.01(s)' on the y-axis (DV). Both axes include the variable names and units, meeting the criterion requirements for properly labeled IV vs DV axis labels.
📷 AN27	Scatter graph contains IV vs DV 'Measurable' axis units.	1	The scatter graph clearly shows IV (splint length) on x-axis with units in cm and DV (burning time) on y-axis with units in seconds. Both axes are properly labeled with measurable units.
📷 AN28	Scatter graph contains IV vs DV axis Instrumental Uncertainty values.	1	The scatter graph's x-axis label clearly states 'Splint length +/- 0.05 (cm)', showing the instrumental uncertainty value with the axis label and units as required by the criterion.
📷 AN29	Scatter graph contains uses crosses to plot data points.	1	The scatter graph uses X-shaped markers (crosses) to plot all data points, as required by the criterion. The crosses are clearly visible at each data point location on the graph.
📷 AN30	A scatter graph trendline gradient equation shows the Final Relationship is given.	1	The graph clearly shows a trendline with an equation y = 6.2355x + 0.4295, which represents the final relationship between splint length and burning time. The student explicitly identifies this as the 'Final Relationship' in the text and uses it throughout their analysis to quantify the relationship (+6.20 s/cm).
📷 AN31	Scatter graph trendline has a R2 value given.	1	The scatter graph clearly displays a trendline with an R² value (R² = 0.9182) visible next to the trendline equation. This meets the criterion requirement for having an R² value given on the scatter graph trendline.
📷 AN32	Horizontal 'Uncertainty bars' for IV are added to the scatter graph, using the IV Instrumental Uncertainty, to graphically show the actual values of t	1	The graph clearly shows horizontal error bars on the x-axis for the independent variable (splint length). These bars are visible extending horizontally from each data point. The student explains in the text that instrumental uncertainty for length is ±0.05 cm, and the graph title specifically mentions 'Uncertainty bars'. The horizontal bars are present and represent the IV instrumental uncertainty as required.
📷 AN33	Vertical 'Uncertainty bars' for DV are added to the scatter graph to graphically show the calculated values of the Uncertainty in Repeats. Any changes	1	Vertical uncertainty bars are clearly visible on the scatter graph at each data point. The student has calculated and displayed uncertainty bars using actual max/min values from their repeat data, resulting in asymmetric bars. The methodology is explained in the text and the bars accurately represent the uncertainty in repeats for the dependent variable.
📷 AN34	A Maximium gradient trendline is calculated from the lowest vertical uncertainty bar and highest horizontal uncertainty bar on the first data point, t	1	The graph clearly shows three trendlines - a main trendline plus maximum and minimum gradient lines above and below it. The yellow line represents the maximum gradient and the blue line represents the minimum gradient, as evidenced by their different slopes and positions relative to the uncertainty bars on the data points.
📷 AN35	A Minimum gradient trendline is calculated from the highest vertical uncertainty bar and lowest horizontal uncertainty bar on the first data point, to	1	The graph clearly shows three trendlines - a main best-fit line (black) and two additional lines (orange and blue) that represent maximum and minimum gradients based on the uncertainty bars. These additional trendlines are properly positioned to account for the uncertainty ranges in the data.
📷 AN36	Trendline equations for the Maximum and Minimum gradient trendlines are shown on the graph.	1	The graph clearly shows three trendlines with their equations: the main trendline (black), maximum gradient trendline (yellow/orange, y = 10.993x - 10.785), and minimum gradient trendline (blue, y = 0.1079x + 26.28). Both maximum and minimum gradient trendline equations are present and legible on the graph.
AN37	Uncertainty in Final Relationship is calculated by [(Maximum gradient value-minimum gradient value)/2 = Uncertainty in Final Relationship] formula.	1	The student clearly shows the uncertainty calculation using the specified formula. Under 'Uncertainty in Final Relationship' they state: 'Using (Max-Min)/2 Formula: (10.99-(-0.11))/2 = +/-5.5 s/cm' and also show an alternative method using actual max/min data. The maximum gradient (10.99) and minimum gradient (-0.11) are clearly identified, and the calculation is correctly performed.
AN38	State Uncertainty in Final Relationship units, using [Y axis units/X axis units] formula.	1	The student clearly states the uncertainty in final relationship as '+6.20 +/- 6 s/cm' in the Analysis section. This follows the required format with numerical uncertainty (±6) and correct units (s/cm) representing Y-axis units (seconds) divided by X-axis units (cm). The calculation method using (Max-Min)/2 formula is shown, and the final value is appropriately stated with units matching the relationship between burning time and splint length.
AN39	State Uncertainty in Final Relationship to 1 Significant Figure	1	The student clearly states the uncertainty in the final relationship as '+6.20 s/cm +/- 6 s/cm (1 sig fig)' which shows the uncertainty (±6) expressed to 1 significant figure. This is explicitly shown in the Analysis section under 'Uncertainty in Final Relationship'. The student calculated this from the max/min gradient data and correctly rounded to 1 significant figure as required by the criterion.
AN40	Convert Uncertainty in Final Relationship into %Uncertainty in Final Relationship using the [Uncertainty in Final Relationship/Final Relationship grad	1	The student correctly applies the formula: (6.09 / 6.20) x 100 = +/- 98%. They show the calculation step-by-step with the uncertainty value (6.09) divided by the final relationship gradient (6.20), multiplied by 100. The result is clearly stated as a percentage (+/- 98%) and even rounded to 1 significant figure (+/- 100%). This meets all requirements of the criterion.
AN41	State %Uncertainty in Final Relationship to 1 Signficant Figure	1	The student clearly states the percentage uncertainty in the final relationship as '+/- 98%' and then correctly rounds it to '+/- 100% (1 sig fig)'. The calculation is shown: '(6.09 / 6.20) x 100 = +/- 98%'. This meets the criterion requirement of stating the percentage uncertainty to 1 significant figure.

Conclusion (9 criteria)

Code	Criterion	AI	Justification
CO1	The research question is answered by describing the IV-DV relationship gradient trend.	1	The student clearly describes the IV-DV relationship based on their trendline data. They state 'The averaged data suggest that as the length of the splint increases, the burning time also increases at +6.20 s/cm' which directly addresses the positive gradient trend between splint length (IV) and burning time (DV). This description is explicitly based on their scatter graph trendline as required by the criterion.
CO2	The IV-DV relationship gradient equation is explicitly stated.	1	The student explicitly states the IV-DV relationship gradient equation multiple times in the report: 'y = 6.2355x + 0.4295' where y is burning time (DV) and x is splint length (IV). The gradient value of 6.20 s/cm is clearly identified and discussed throughout the analysis and conclusion sections, meeting the criterion requirement.
CO3	The IV-DV relationship gradient units are quoted in the conclusion.	1	The conclusion clearly states the gradient relationship between IV and DV as '+6.20 s/cm' (seconds per centimeter), which represents how burning time increases with splint length. The units 's/cm' are explicitly stated multiple times in the conclusion section, including with uncertainty values '+6.20 s/cm +/- 100%'. These are appropriate units for the time-length gradient relationship.
CO4	Comment on gradient R2 value in terms of strength of correlation. (weak <0.3, moderate 0.3-0.7, strong >0.7)	1	The student explicitly states the R² value (0.91) and correctly categorizes it as a 'strong correlation' which aligns with the criterion's requirement of strong >0.7. The statement appears in the Conclusion section: 'The correlation coefficient R2 value is 0.91, making this not perfect but still a strong correlation.' This directly addresses all requirements of the criterion.
CO5	Accuracy of relationship is justified based on cited research of a similar area of study.	1	The student accurately describes the combustion relationship and provides justification citing research from 'Is Fuel Reduction Burning the Answer?' about forest fires doubling spread rate with doubled fuel. While the cited research is from forest fires rather than single splint burning, the student explicitly acknowledges this difference and uses it to explain discrepancies. The citation is properly formatted in MLA style and is relevant enough without being too similar to suggest plagiarism.
CO6	Hypothesis is re-stated and compared with final results and commented on in terms of trend and speculation as to the underlying chemistry causing this	1	The student restates their hypothesis in the CO6 section ('confirm my initial hypothesis'), compares it with results (positive gradient of +6.20 s/cm), and comments on the trend (strong positive, linear relationship). They reference the underlying chemistry concept that 'more fuel must take longer to burn in a combustion reaction,' which connects back to their original hypothesis about increased fuel requiring longer burning times.
CO7	% Uncertainty in Final Relationship from min-max trendlines is re-stated in the Conclusion.	1	The student clearly restates the % Uncertainty in Final Relationship (98% or 100% to 1 sig fig) in the Conclusion section under CO7. They write: 'The Uncertainty in Final Relationship is very large at 98%, highlighting the presence of uncontrolled variables...' This directly references the percentage uncertainty calculated earlier from the min-max trendlines variation.
CO8	The magnitude of the %Uncertainty in Final Relationship gradient to potentially change the trend direction and invalidate the conclusion is commented	1	The student explicitly discusses the 98% uncertainty in the final relationship gradient in the CO7-CO9 section, stating: 'These very large Uncertainty in Final relationship uncertainty bars... The trendline seems almost surely to be still increasing, despite a small possibility that the trendline could indeed be horizontal (or very unlikely negative).' This directly addresses how the uncertainty magnitude could potentially change the trend direction and invalidate the conclusion.
CO9	Any concerns making the result invalid have been commented on. If the experiment has no obvious problems in its logic, leading to an invalid conclusio	1	The student addresses validity concerns in CO7-CO9, discussing how uncontrolled variables (particularly burning rate) and large uncertainties could affect results. They acknowledge the relationship might be horizontal despite appearing positive. In EV4, they identify potential systematic errors from inconsistent burning methods that could invalidate conclusions. The report demonstrates awareness of major experimental flaws that could compromise validity.

Evaluation (13 criteria)

Code	Criterion	AI	Justification
EV1	Strengths of methodology are highlighted, based on trial run modifications if possible.	1	The student identifies a clear strength in EV1: 'removal of data for splints that only burned partially as this would cause increased Uncertainty in Repeats 'error bars' and make the trend less certain.' This strength is linked to trial run modifications mentioned in RD22 where they discovered splints sometimes extinguished prematurely and updated their method accordingly.
EV2	Equipment choice is evaluated to reduce Instrumental Uncertainties.	1	The student evaluates equipment choice in EV2 by analyzing instrumental uncertainties of the ruler (±0.05cm) and timer (±0.01s), concluding these are insignificant compared to methodological uncertainties. They identify that changing to more precise equipment would not significantly improve results since the propagated uncertainty (0.6%) is much smaller than the uncertainty in final relationship (100%). This addresses how equipment contributes to combined uncertainties and evaluates their relative importance.
EV3	Comparison of a Mean Propagated % Instrumental Uncertainty vs % Uncertainty in Final Relationship from gradients is stated using [Mean Average IV % un	1	The student explicitly compares Mean Propagated % uncertainty (0.6%) vs % Gradient Uncertainty in Repeats (100%) in the EV3 section. They calculate the mean propagated uncertainty from average IV and DV uncertainties (0.56% + 0.02% = 0.58%) and compare it to the final relationship uncertainty (98-100%). They explain why the final uncertainty is two orders of magnitude larger, discussing outliers and methodology issues.
EV4	Major Methodological improvements suggested to improve accuracy and validity by identifying and removing specific Systematic errors that have become a	1	The student identifies major systematic errors that could make the experiment invalid (burning technique variations, unspecified ignition method) and suggests specific methodological improvements to address them (keeping splints vertical, specifying exact ignition procedures). These are presented in EV4 and the detailed table, showing how lack of method standardization created systematic errors affecting validity.
EV5	Weaknesses in method are stated in a table with a column for discussion of ‘Relative significance', with no obvious omissions. Minor = negligible eff	1	The student provides a comprehensive table under 'Weaknesses in method' that lists four problems with columns for Error Type, Impact and Relative Significance, and Potential solutions. The relative significance is clearly stated for each weakness (Minor, Moderate, Major) with appropriate justifications. The table meets all requirements with no obvious omissions.
EV6	Weaknesses in method are stated in a table with a column for ‘Error Type' and are correctly identified, with Systematic Errors only producing errors o	1	The student provides a comprehensive table under 'Weaknesses in method' (EV5-EV8) with an 'Error Type' column. Errors are correctly categorized - Systematic Errors (burning technique, ignition method) are described as producing consistent effects in the same direction, while Random Errors (flame extinguishing) are described as unpredictable. The table meets all requirements with proper error type identification and descriptions matching the criterion's definitions.
EV7	Weaknesses in method are stated in a table with a column for ‘Problems'.	1	The student presents a clear table under 'Weaknesses in method' (EV5 EV6 EV7 EV8) with a column explicitly labeled 'Problems with current method'. The table contains four detailed entries identifying specific methodological issues: burning technique variations, premature flame extinction, subjective ignition timing, and non-specific ignition methods. Each problem is clearly articulated with explanations of the issues.
EV8	Weaknesses in method are stated in a table with a column for ‘Suggested Solutions'.	1	The student presents a clear table under 'EV5 EV6 EV7 EV8 Weaknesses in method' with four columns: 'Problems with current method', 'Error Type', 'Impact and Relative Significance', and 'Potential solutions'. Each weakness is paired with a suggested solution that addresses future experimental improvements, meeting the criterion's requirements for a table format with suggested solutions column.
EV9	Improvements suggest increased Repeated data points and removal of outliers to reduce Random Errors, causing smaller Uncertainty in Repeats.	0	While the student mentions not removing outliers and using visual identification (AN11-12), they fail to explain the two distinct processes required: (1) how additional data points lead to lower standard deviation, and (2) how this narrower range then allows outlier identification. The report simply states outliers were kept without demonstrating understanding of how increased repeats would reduce uncertainty through these mechanisms.
EV10	Improvements suggested to expand the IV data range are made.	1	The student explicitly suggests expanding the data range to include longer splints (20-30cm) in EV10, providing specific values beyond the original 2-16cm range. They explain this would make the trend easier to observe and consider practicability issues like rigidity and safety concerns. This meets all requirements: specific values suggested, link to trend observation, and consideration of practicability.
EV11	Improvements suggested to narrow the IV data intervals are made.	1	The student explicitly suggests reducing IV intervals from 2cm to 0.5cm (2.0, 2.5, 3.0, 3.5cm etc.) under EV11, comparing with existing values and explaining this would 'allow for a more consistent trendline to be produced.' They link this to increasing fine detail in the relationship. While brief, it meets the criterion's requirement for specific values and connection to trendline accuracy.
EV12	Minor Methodological improvements suggested to improve on the accuracy of the experiment.	1	The student provides specific methodological improvements to increase accuracy: specifying how to hold splints (leave 1cm for holding), defining endpoint clearly, adding detailed instructions like 'burn at only one end', 'hold at specific angle', and 'maximize burn time'. They explain how these changes would reduce systematic errors and increase consistency/accuracy. The suggestions are feasible and directly address identified limitations in their current methodology.
EV13	Suggested extension investigations, that will adapt and improve this specific investigation are proposed.	1	The student proposes an extension investigation examining how wood thickness affects combustion rate, relating it to forest fire spread in younger saplings. This directly builds on the original experiment by testing a different dimension variable while maintaining the combustion focus. The justification explains how this would provide insight into whether thinner branches burn faster, which could refine conclusions about wood combustion beyond just length effects.