Provides answers to commonly asked questions about COBRA. Health Benefits Under the Consolidated Omnibus Budget Reconciliation Act (COBRA) (PDF) Provides a detailed overview of the major provisions of COBRA.
In the two-sample pooled t-test the pooled variance is computed by averaging the two individual sample variances. The assumptions for the two-sample pooled t-test for the difference in two means are that there are random samples from two independent normal populations with common but unknown variance.
The t test is a two-tailed test because the tail of the distribution on each side of the mean is analyzed. For many laboratory measurements or clinical trials, one would want a two tailed test because the value or the outcome could be either above or below the mean.