The sample t-test, often referred to as the t-test, is a statistical test used to compare the means of two groups or samples to determine if there are significant differences between them. There are three primary types of sample t-tests: independent samples t-test (for comparing the means of two independent groups), paired samples t-test (for comparing the means of two related groups or the same group under different conditions), and one-sample t-test (for comparing the mean of a single sample to a known population mean or a specified value).