Desirable to use them if possible. However, data must meet a number of assumptions to be able to use parametric statistical procedures.

In Unit III, you developed your research design, or blueprint, for the research project. It is now time to begin working the plan by working with the data. In Unit IV, you will describe the data to determine if assumptions for parametric testing are met.

Parametric tests are more powerful and superior to non-parametric tests, so it is desirable to use them if possible. However, data must meet a number of assumptions to be able to use parametric statistical procedures.

Although assumptions vary by statistical procedure, nearly all statistical tests require the assumption of normality, or a normal distribution of data. When plotted, normality is represented by a bell-shaped curve. This is one of several assumptions you will test for in Unit IV.