S2.1.2—Designing investigations
- Syllabus
- First assessment 2025
- Objective
- S2.1.2
- Level
- HL
Design an Investigation
Design backwards from the evidence needed
Choose whether a hands-on experiment, database, simulation or model can answer the research question. Then specify how the independent variable will be changed, the dependent variable measured and relevant control variables held constant.
| Design choice | What to justify |
|---|---|
| Independent-variable range | Wide enough to reveal the expected relationship, safe and within apparatus/model limits |
| Number and spacing of values | Sufficient to show a trend or shape without clustering all evidence in one region |
| Repeats | Enough to reveal random variation and support a representative value |
| Measurement method | Apparatus, resolution, sequence, timing, geometry and how each value is obtained |
| Control variables | Why each could affect the dependent variable and how it will be kept constant |
Pilot before fixing the method
A short pilot checks whether the range produces measurable changes, whether the apparatus resolution is adequate and whether the sequence is practical. Use its observations to revise the method; do not invent or discard results to fit the hypothesis.
A valid method changes one intended cause at a time
Give enough procedural detail for another student to reproduce the investigation. A larger range, more readings or different technology is an improvement only when it strengthens the evidence for the stated relationship.
S2.1.2 Exam Analysis
Assessment in practice
1 marksHow it is assessed
Questions identify a control variable or suggest widening a star-temperature range.
Command terms
State / Suggest
What earns marks
Name a measurable variable to keep constant, or state that a wider range improves the test of the relationship.
Watch for
Naming an uncontrolled or irrelevant quantity, or proposing more precision without improving the range.
Retrieve Investigation Design
Design from a question
Turn context into a measurable question, hypothesis and prediction with independent, dependent and controlled variables.
Make evidence reliable
Choose a useful range and repeats, calibrate instruments, control relevant conditions and reduce or correct known losses and background.