A student is investigating the effect of temperature on the rate of an enzyme-controlled reaction. They plan to measure the time taken for a substrate to be completely broken down at different temperatures. Describe how the student could ensure their results are reliable.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
1. Perform several trials at each temperature to allow for reproducibility.
2. Calculate the mean time for each temperature from the repeated trials.
3. Identify any outliers or anomalous results and exclude them before computing the mean.
4. Keep all other independent variables (substrate concentration, pH, enzyme amount, reaction volume, etc.) constant across all trials.
2. Calculate the mean time for each temperature from the repeated trials.
3. Identify any outliers or anomalous results and exclude them before computing the mean.
4. Keep all other independent variables (substrate concentration, pH, enzyme amount, reaction volume, etc.) constant across all trials.
Examiner tips
- Use the word "mean" or "average" to show calculation of central tendency.
- Show that you have repeated the experiment and that you have controlled other variables.
- Mention outlier removal to demonstrate data handling skills.
Common mistakes
- Failing to repeat trials, giving only one measurement per temperature.
- Not stating that other variables are held constant.
- Including anomalous data in the mean without justification.
Mark scheme (4 marks)
- Repeat the experiment multiple times at each temperature investigated.
- Calculate a mean or average value from the repeated trials for each temperature.
- Identify and exclude any anomalous results or outliers before calculating the mean.
- Ensure all other independent variables are kept constant across all trials.
Related
- All OCR A-Level Biology A (H420) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →