Nonparametric Analysis of Variance Analysis of variance is sensitive to the distribution of the error term. If the error term is not normally distributed, the statistics based on normality can be misleading. The traditional test statistics are called parametric tests because they depend on the specification of a certain probability distribution except for a set of free parameters. Parametric tests are said to depend on distributional assumptions.
Nonparametric methods perform the tests without making any strict distributional assumptions.
Even if the data are distributed normally, nonparametric methods are often almost as powerful as parametric methods. The NPAR1WAY procedure performs a nonparametric one-way analysis of variance. All rights reserved.