Nonparametric statistics

Statistics

Parametric statistics

Skewness

Econometrics

Paleontology

Kurtosis

Normality

Test (biology)

Mathematics

Normality test

Biology

Statistical hypothesis testing

International Journal of Assessment Tools in Education

Checking the normality assumption is necessary to decide whether a parametric or non-parametric test needs to be used. Different ways are suggested in literature to use for checking normality. Skewness and kurtosis values are one of them. However, there is no consensus which values indicated a normal distribution. Therefore, the effects of different criteria in terms of skewness values were simulated in this study. Specifically, the results of t-test and U-test are compared under different skewness values. The results showed that t-test and U-test give different results when the data showed skewness. Based on the results, using skewness values alone to decide about normality of a dataset may not be enough. Therefore, the use of non-parametric tests might be inevitable.

Parametric or Non-parametric: Skewness to Test Normality for Mean Comparison