t-Test, Paired Samples

Before describing a paired samples t-test, it is helpful to offer a brief reminder of the t-test itself. The t-test statistical procedure is used when a researcher wants to know whether two group means are different and whether that difference can be shown to be statistically significant. Statistical significance indicates that the outcome of the statistical procedure is rare enough to confirm that the differences observed would not have occurred solely by chance. For communication research (and many other social sciences), a one in 20 chance is usually considered sufficiently rare. Thus, the alpha (or significance) level for most t-tests is set at .05.

The paired samples t-test is one of three main types of t-tests, the other two being the one-sample t-test ...