What Does a T-Test Measure?

The T-test is a statistical test that measures the significance of the difference between the means in two sets of data in relation to the variance of the data.

The T-test can be used to determine whether two samples are statistically different when each small group of data is taken from distinct populations, the results from each group are not dependant on the results from the other group and the distribution of data in both groups is considered to be normal (determined by normality test). However, the T-test is not suitable for evaluation of three or more variables (analysis of variance is used in this case) or for evaluating large sets of data (the Z-test should be used for large samples).