How can nonparametric tests be defined?

Nonparametric tests can be defined as statistical methods that do not require the data to conform to a specific distribution, particularly the normal distribution. This characteristic allows nonparametric tests to be used on a variety of data types, including ordinal and nominal data, rather than being limited to interval or ratio data, which are typically required for parametric tests. As a result, nonparametric tests are especially useful when the sample sizes are small or when the data do not meet the assumptions of normality, enabling robust analyses even in less-than-ideal conditions. This flexibility makes nonparametric tests a vital option for many researchers and practitioners who deal with real-world data that may not fit traditional statistical assumptions.