Exam Strategy
Statistics · AP · Inference for Categorical Data — Chi-Square
CED focus
Introducing Statistics: Are My Results Unexpected?
This topic is assessed on the AP Exam.
Multiple-choice tips
- Match procedure to parameter and design before calculating.
- Match χ² GOF vs homogeneity vs independence from the table setup.
- Eliminate expected-count violations in MC.
- Check whether a proportions z-test is inappropriate.
- Identify which cells drive a large χ² in MC.
Free-response tips
- Use State–Plan–Do–Conclude with conditions and context throughout.
- State hypotheses about distributions or association in words.
- Show expected counts or use calculator χ² output with labels.
- Conclude about the population in context.
- Link conclusion back to the research question.
Common traps
- ‘Accept H₀’ wording or skipping conditions
- Using a z-test when χ² is required
- Skipping expected-count condition
- Confusing homogeneity and independence wording
Quick checklist
- [ ] Can choose the correct χ² procedure
- [ ] Can check expected counts
- [ ] Can conclude about association in context