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6.1.2Inquiry Process

Designing in Biology — IB Biology HL Revision Notes & Topical Questions

5 min read 5 parts Lesson 154 of 160

📚 IB Biology HL Hub / Topical Revision
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Part 1 of 5Elements of a Good Design

6.1.2 Designing in Biology
Variables
  • The independent, dependent and controlled variables are identified,
    • and the way each will be changed, measured or kept constant is described.
Range of the independent variable
  • At least five values spread evenly over a sensible range allow a trend to be seen and a graph to be drawn.
Repeats
  • At least three repeats at each value allow a mean to be found and an anomaly to be recognised.
Sample size
  • When using living organisms, enough individuals are chosen to reduce the effect of natural variation.
Materials
  • A list of the apparatus, quantities and concentrations makes the method reproducible by another person.

Part 2 of 5Turning the Plan into a Method

1
Write the method as numbered steps in the past or in the imperative, with quantities, sizes and times stated clearly.
2
Describe how each variable will be measured, including the instrument and its resolution.
3
Run a pilot trial to test the method, and adjust ranges, volumes or times if the readings are too small, too large or too fast.
4
Plan how data will be recorded and analysed, so that the method gives the data needed to answer the question.
5
Make sure the method has a safety and ethical assessment, with each hazard linked to a precaution.
Design featureReason
At least five values of IVReveals the trend
At least three repeatsAllows a mean and detection of anomalies
Pilot trialTests the practicality of the method

Part 3 of 5Judging the Quality of the Design

Judging the Quality of the Design
Sufficient data
  • Enough data are collected to answer the question without being so much that the work becomes unmanageable.
Relevant data
  • Each measurement is linked to the research question, avoiding unnecessary extras.
Feasibility
  • The plan can be completed with available time, equipment and skills.
Reproducibility
  • Sufficient detail is given for another investigator to repeat the work.

Part 4 of 5Worked Example

Question

  • A student plans to test the effect of temperature on yeast respiration using 5 temperatures, 3 repeats per temperature, and each trial takes 10 minutes.
  • How long do the trials take in total?

  1. Number of trials = 5 × 3 = 15.
  2. Time = 15 × 10 minutes = 150 minutes.
  3. Convert to hours150 ÷ 60 = 2.5 hours, so the trials must be shared across more than one lesson or run at the same time.

Answer The trials need 150 minutes (2.5 hours), so the plan must allow for this when judging feasibility.

Part 5 of 5Exam Checklist & Tips

6.1.2 – Key Points for the Exam

  • Pilot trial A small preliminary run to test and improve a method.
  • Repeat Doing the same measurement again under the same conditions.
  • Reproducibility The ability of others to obtain the same results using the same method.
  • Feasible Possible to carry out with the available time and resources.

Common Mistakes

  • Choosing fewer than five values of the independent variable.
  • Writing the method as a general description instead of detailed steps.
  • Not stating the instrument or its resolution for the measurements.
  • Skipping a pilot trial and then finding the method unworkable.

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