Evaluate Email Subject Line Performance Using Hypotheses

##### Scenario Email marketing team wants to evaluate the performance of a new subject line. ##### Question Define the null and alternative hypotheses for comparing click-through rates between control and test emails. Explain how the Central Limit Theorem justifies using a z-test in large samples. Derive the sample size needed to detect a 2-percentage-point lift with 80% power at α = 0.05. ##### Hints Think proportions, pooled variance, power formula.