Under the correct circumstances a nonparametric tests can be as powerful as a parametric test.

Question

Quizplus · Accepted Answer

Nonparametric tests can be as powerful as parametric tests when the assumptions of normality and equal variance are not met, or when the sample size is small. In such cases, nonparametric tests may have the advantage of not making strict assumptions about the shape of the distribution, and may be more robust to outliers. Therefore, it is not accurate to say that parametric tests are always more powerful than nonparametric tests.

Under the Correct Circumstances a Nonparametric Tests Can Be as Powerful