Choosing an inference procedure

Why Procedure Selection Drives Your AP Score

Inference from Units 3 and 4 is a big part of the exam. In Section II, Free-Response Question 3 (10 raw points, 12.5% of your total exam score) is entirely dedicated to a complete hypothesis test or confidence interval, and Question 4 can include conditions, interpretations, or steps of an inference procedure. In Section I, Units 3 and 4 (which also cover sampling distributions) together make up 25–45% of the 42 multiple-choice questions (Unit 3: 15–25%; Unit 4: 10–20%).

Because AP Statistics Free-Response questions use analytic (point-by-point) scoring, misidentifying the procedure at the start of Question 3 can cost you several points at once (for example the procedure, parameter, condition and calculation points), because they all depend on choosing the right procedure.

The 4-Question Decision Protocol

Whether you have 15 seconds on a Section I multiple-choice stem or 2 minutes to plan Section II Question 3, run every problem through these four questions in exact order:

1. What is the variable type?
   • Categorical (counts, yes/no, proportions, categories in a two-way table) $\rightarrow$ Unit 3 ($z$-procedures for proportions or $\chi^2$ tests).
   • Quantitative (numerical measurements where an average makes sense, means $\mu$, standard deviations $s$) Unit 4 (-procedures for means).

Complete Procedure Matrix (Units 3 & 4)

Learn the names in the Official Procedure Name column (equivalent correct wording, such as “one-proportion $z$-test”, is also accepted). A vague name like “$z$-test” or “two-sample test” does not say which procedure you mean, so it may not earn the procedure-identification point.