# Statistics/Testing Data/t-tests2

In both the one- and two-tailed versions of the small two-sample t-test, we assume that the means of the two populations are equal. To use a t-test for small (independent) samples, the following conditions must be met:

- The samples must be selected randomly.
- The samples must be independent.
- Each population must have a normal distribution.

A small two sample t-test is used to test the difference between two population means μ_{1} and μ_{2} when the sample size for at least one population is less than 30. The standardized test statistic is: