The rest of the article, however, discusses understanding the two-sample t-test, which is easy to use but not so easy to understand. If one subtracts the means from two samples, in most cases ...

A t-test for population means compares the means between two populations. It is appropriate when the population standard deviations are unknown. This applet allows users to change the distributions of ...

A two-sample z-test for population means compares two population means. It is appropriate when the population standard deviations are known and the sample sizes are large. This web calculator conducts ...