S2.3 Concluding and evaluating

Syllabus
First assessment 2025
Topic
S2.3
Level
SL

Justify Conclusions

A conclusion is a bounded answer to the research question

State the measured relationship or result, cite the processed evidence that supports it and say whether the stated hypothesis is supported, contradicted or remains unresolved. Do not repeat the procedure.

Part of the conclusion What to include
Claim Direct answer using the investigated variables and conditions
Evidence Gradient, intercept, calculated value, pattern or comparison from processed data
Uncertainty Whether uncertainty bars/ranges allow competing interpretations and how strongly the claim is supported
Scientific context Comparison with the accepted model, value or explanation, including relevant assumptions
Scope The range and system for which the evidence applies

Example — evaluating an inverse model

If a hypothesis predicts y1/xy\propto1/x, values of xyxy that clearly vary beyond their uncertainties contradict that prediction. Values that are approximately constant are consistent with the model, but they do not prove it: another relationship may also fit the limited range.

Uncertainty controls confidence, not truth

Agreement within stated uncertainty supports consistency with an accepted value; disagreement outside it flags tension, underestimated uncertainty or systematic effects. Neither result alone proves the model or identifies the cause.

S2.3.1 Exam Analysis

Assessment in practice

1 marks
How it is assessed

Questions outline a conclusion about Stefan–Boltzmann law or state a conclusion based on a result and its uncertainty.

Command terms

Outline / Suggest

What earns marks

Refer to the observed relationship or value and explicitly use uncertainty or accuracy evidence.

Watch for

Repeating a result without interpreting it or claiming agreement without the uncertainty comparison.

Evaluate Errors and Improvements

Evaluate by tracing cause → measurement → result → conclusion

Name a specific random or systematic effect, explain which measurement it changes and in what direction when known, then state how the processed result and conclusion are affected. A label such as “human error” is not an evaluation.

Issue Impact on evidence Targeted response
Random variation in timing Repeated values spread; the representative value is less precise Repeat under the same conditions and use the spread/mean appropriately
Positive instrument zero offset Every affected reading is shifted; it may cancel in a difference or gradient, so trace the calculation before claiming bias Zero/calibrate first or apply a justified correction
Heat lost to surroundings in water heating Input energy is treated as if all entered the water, so calculated specific heat capacity is too high Insulate and account for energy absorbed by the container where the method permits
Limited range or model assumption The apparent relationship may hold only over the tested range or omit a relevant physical feature Extend the justified range or revise/test the assumption

Evaluate the hypothesis, not just the apparatus

Use trend, intercept, uncertainty bars and alternative explanations to state whether the evidence supports or contradicts the hypothesis. A best-fit line missing some uncertainty bars weakens the proposed model; an approximately constant transformed quantity is compatible with a model but cannot prove it.

Make improvements specific and realistic

For each weakness, name the physical change, how it reduces or measures the stated effect and why the conclusion becomes stronger. “Be more careful” and unrelated extra repeats do not correct a systematic bias or an unrealistic assumption.

S2.3.2 Exam Analysis

Assessment in practice

1–2 marks
How it is assessed

Questions explain the effect of heat loss or evaporation on calculated specific heat capacity and identify how scientific work gains support.

Command terms

Outline / Identify

What earns marks

Name the mechanism, predict the direction of bias, or choose independent peer review when the question asks how validity is supported.

Watch for

Naming heat loss without its effect on the calculated value or choosing instrumentation improvement when the question asks about independent scientific support.

Retrieve Evaluation Practice

Conclude from evidence

Answer the question, refer to the trend or value, and compare with uncertainty and the model.

Evaluate causally

Name the error or limitation, predict its effect, and propose an improvement that targets it realistically.