StatisticsdrillA/B test: p-value and decision
A statistics problem from Statisticsdrill. Solve it with one answer box, with a fresh sample on every attempt and the worked steps and spreadsheet function in the answer, and it is checked the moment you submit.
The task
An A/B test of a signup form: control 177 signups out of 1,500 visitors, variant 174 out of 1,200. Using a two-sided two-proportion z test with a pooled standard error, what is the p-value? Then decide at α = 0.05. Round to 4 decimal places.
What this problem teaches
Decide the sample size and α before the test starts. Checking the p-value every day and stopping at the first small one inflates false positives.
A hint if you get stuck
Pool the rates for the standard error, find z for (B - A), then p = 2 × (1 - Φ(|z|)).
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