Let and be the sample standard deviations constructed from and , respectively. When it is reasonable to assume `` ,'' we can construct the pooled sample variance
Confidence interval. The following table shows the corresponding confidence interval of the population mean difference , when your null hypothesis is rejected.
|Hypothesis testing||-level confidence interval|
Example. Suppose that we consider the significant level , and that we have obtained and from the control group of size , and and from the experimental group of size . Here we have assumed that . Then we can compute the square root of the pooled sample variance , and the test statistic