t-TESTS AND PROCEDURES
t-Tests for the Significance of the Difference between the Means of Two Samples.
The first of these pages is somewhat more streamlined than the other two. It will also more comfortably handle large sample sizes. Although the other pages are somewhat clunkier, their data-entry format might prove more fail-safe for the beginning student. As the latter two pages open, you will be prompted to enter the size of your samples.
t-Test for Independent or Correlated SamplesT
t-Test for Independent Samples [cell-entry format]T
t-Test for Correlated Samples [cell-entry format]

For non-parametric alternatives to the independent and correlated samples t-tests, see the Mann-Whitney Test and the Wilcoxon Signed-Ranks Test under Ordinal Data.