Scientific Inquiry and Investigation Skills
Scientific Inquiry and Investigation Skills is the domain that asks you to plan fair tests, choose measurements, organize data, and justify conclusions. Exam items typically give a scenario and ask which variable changed, whether the method was valid, or what a graph shows.
Core rules
- A hypothesis is a testable explanation, not a guess or a prediction. A prediction states what you expect if the hypothesis is supported.
- The independent variable is changed deliberately; the dependent variable is measured; controlled variables are kept constant.
- Reliability improves with repeated trials and larger samples. Validity depends on controlling confounders and measuring what you claim to measure.
- On a graph, put the independent variable on the x-axis and the dependent variable on the y-axis; label units and use a sensible scale.
Worked example
A student tests whether fertilizer affects bean growth. She grows one bean plant with fertilizer and one without, both in identical pots, soil, light, and water, for four weeks, and measures plant height. Fertilizer amount is independent; height is dependent; light, water, soil, pot size, and plant type are controlled. One plant per group is a weakness because a single plant may be unusual, so she should repeat with several plants per group. She should report means and compare variation, not just say the fertilizer works.
Traps that cost marks
Calling a prediction a hypothesis; changing two variables at once; measuring with inconsistent units; treating a single trial as conclusive; saying data prove a hypothesis rather than support or fail to support it; ignoring an outlier without justification.