Hypothesis Testing: Two Samples

To compare two means or two proportions, one works with two groups.

To compare independent samples, both populations are normally distributed with the population means and standard deviations unknown.

If two estimated proportions are different, it may be due to a difference in the populations or it may be due to chance.

In a hypothesis test for matched or paired samples, subjects are matched in pairs and differences are calculated.

In order to compare two variances, we must use the $F$ distribution.

A common problem is calculating the sample size required to yield a certain power for a test, given a predetermined type I error rate $\alpha$.