Two-Sample t-Test for Independent or Correlated Samples. The independent-samples version performs both the "usual" t-test, which assumes that the two samples have equal variances, and the alternative t-test, which assumes that the two samples have unequal variances.T [Traducción en español]T

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. For small samples, see also 'Resampling Probability Estimates ...' under Miscellanea.

Single Sample t-Test. For the significance of the difference between the observed mean of a sample and a hypothetical mean of the population from which the sample is randomly drawn. .95 and .99 Confidence Intervals for the Estimated Mean of a Population. Given a sample of N values of X, randomly drawn from a normally distributed population, this unit will calculate the .95 and .99 CIs for the estimated mean of the population.