AP Statistics · Unit 3 · Topic 3.7

Carrying Out a Test for a Proportion Study Lab

Put it all together: hypotheses, conditions, test statistic, p-value, and a conclusion in context. Change any input and the full four-step answer rewrites itself, so you can see exactly how each piece connects.

1. One-sample z-test for a proportion, start to finish

Enter the study details. The lab checks the conditions, does the calculations, and writes a full four-step answer (State, Plan, Do, Conclude) the way an AP grader wants to see it.

z = (p̂ − p₀) ÷ √( p₀(1 − p₀) ÷ n )
Preset studies
Alternative
Significance level

Standard normal model

p-valueObserved zCutoff for α
p̂
z
p-value
Decision

2. Key ideas

State

Hypotheses and α

Write H₀ and Hₐ about p, define p in context, and give α.

Plan

Name it and check it

One-sample z-test for p. Check Random, 10% (n ≤ 0.1N), and Large counts with p₀ (np₀ ≥ 10 and n(1 − p₀) ≥ 10).

Do

Test statistic

z = (statistic − parameter) ÷ (SD of statistic) = (p̂ − p₀) ÷ √(p₀(1 − p₀)/n). It counts how many SDs p̂ is from p₀.

Do

p-value

Find the area under the standard normal beyond z in the direction of Hₐ; double it for ≠.

Conclude

Link, decide, context

"Because the p-value of 0.015 is less than α = 0.05, we reject H₀. There is convincing evidence that …"

Calculator

1-PropZTest

The calculator gives z and p, but on the FRQ you must still show the formula with numbers and state the conditions.

3. Quick reference

The four steps and what graders look for in each.

StepWhat to writeExample
StateH₀, Hₐ, α, parameter in contextH₀: p = 0.10, Hₐ: p > 0.10, α = 0.05; p = true proportion of all students at the school who are left-handed
PlanProcedure name and three conditionsOne-sample z-test for p; random sample; 150 ≤ 240; 15 and 135 ≥ 10
Dop̂, z formula with numbers, p-valuep̂ = 0.1533; z = (0.1533 − 0.10)/0.0245 = 2.18; p = 0.0147
ConcludeCompare p to α, decision, context0.0147 < 0.05, reject H₀; convincing evidence that more than 10% are left-handed

4. On the FRQ

How to earn the points

  • Every step counts. Missing conditions or context costs points even with correct calculations.
  • Show the test statistic formula with values substituted before giving z.
  • Write the p-value as a probability statement: P(Z ≥ 2.18) = 0.0147.
  • In the conclusion, explicitly compare: "p-value 0.0147 < α = 0.05."
  • Use "convincing evidence" (or "not convincing evidence") and finish with the population parameter in context.

Common mistakes

  • Using p̂ in the standard deviation of a test (that's for intervals).
  • Concluding "H₀ is true" or "accept H₀" when failing to reject.
  • Writing conclusions about the sample instead of the population.
  • Forgetting to double the tail area for a two-sided test.
  • Listing conditions by name without checking them with the actual numbers.

5. Practice questions

AP-style multiple choice. Pick an answer to see the explanation.

0 / 0 correct

6. Key terms

The vocabulary for topic 3.7. Read the list, flip through flashcards, or quiz yourself. For every term in the unit, see the Unit 3 terminology guide.