Читать книгу Methods in Psychological Research - Annabel Ness Evans - Страница 86

The simplest experiment involves two groups, an experimental group and a control group. The researchers treat the groups differently (the IV) and measure their performance (the DV). The question, then, is “Did the treatment work?” Are the groups significantly different after receiving the treatment? If the research involves comparing means from two groups, the t test may be the appropriate test of significance. Be aware that the t test can also be used in nonexperimental studies. For example, a researcher who compares the mean performance of women with that of men might use a t test, but this is not an experiment.

Typically, a researcher will report the group means, whether the difference was statistically significant, and the t-test results. In essence, the t test is an evaluation of the difference between two means relative to the variability in the data. Simply reporting the group means is not enough, because a large difference between two means might not be statistically significant when examined relative to the large variability of the scores of each group. Alternatively, a small difference between two means may be statistically significant if there is very little variation in scores within each group. The t test is a good test when you want to compare two groups, but what if you have more than two groups?