Unit 3 is 15–25% of Section I and the heart of Question 3. Learn the four steps: state, plan, do, conclude.
Weight
15–25% of the multiple-choice section
Topics
3.1 to 3.15
Which standard error
Interval for p: use p̂.
Test for p: use p₀.
Test of p₁ = p₂: pool.
Interval for p₁ − p₂: do not pool.
Reading results
The p-value assumes H₀ is true.
Fail to reject is not proof of H₀.
Lowering α lowers power; a larger sample raises it.
Try 3 questions
Question 1
A city says 30% of its streetlights are LED. An inspector suspects the true proportion is lower and will test this with a random sample of streetlights. Which hypotheses are correct, where p is the proportion of all the city's streetlights that are LED?
Question 2
Which change would increase the power of a significance test, with everything else unchanged?
Question 3
For a test of H₀: p₁ = p₂, why is a pooled sample proportion used in the standard error?