Mathematics Standard • Year 12 • Module 5 • Lesson 4
Causation and Correlation, Build
Scaffolded Practice for Causation and Correlation. Work through each self-contained problem, show your reasoning, then open the worked answers to check your method.
1. Core skill
A survey finds that people who carry umbrellas are more likely to wear raincoats. Does this show that carrying an umbrella causes raincoats to be worn? Identify a likely common cause. 2 marks
2. Use the idea
A school observes a positive association between hours spent in a study group and exam marks. Give two reasons this observational association alone does not prove study groups cause higher marks. 3 marks
3. Check your reasoning
Define a confounding variable in one sentence and apply the definition to the study-group example. 2 marks
Self-check
For each problem, check that your answer includes the requested variable, units or contextual interpretation.
1. Core skill (2 marks)
No. Rain is a plausible confounding variable: it increases the chance of carrying an umbrella and wearing a raincoat, creating an association between the two.
2. Use the idea (3 marks)
Students who attend may already be more motivated or have stronger prior achievement; these are possible confounders. Higher-achieving students may also choose study groups, so direction may be reversed. The survey did not randomly assign participation.
3. Check your reasoning (2 marks)
A confounder is a third variable associated with both the explanatory and response variables that can help explain their observed association. Prior motivation could affect both joining a study group and exam marks.