Parametric statistical methods, like the Student t-test or goodness-of-fit test, assume that data follows a specific distribution, enabling robust hypothesis testing and estimation.

In biostatistics, parametric statistics are frequently used, for instance, when comparing mean blood sugar levels among patients on different treatments.

Conversely, nonparametric statistics do not make any assumptions about the data's distribution.

They are useful when data fails to meet parametric test requirements or is ordinal or categorical.

These methods offer numerous advantages, including robustness to outliers and wider data applications.

However, they tend to be less useful than parametric tests under parametric assumptions.

For instance, using nonparametric statistics, the Wilcoxon rank-sum test compares median survival times between two groups of lab animals.

The Kruskal-Wallis test, another nonparametric alternative to ANOVA, ranks random samples from three or more populations to determine whether their medians are similar.