Nonparametric Statistical Analysis
- Refers to the use of statistical tests or methods when the data being studied comes from a sample or population of people that does not follow a normal distributed.
- Assumes patient population being studied is not normally distributed (i.e., as seen with outliers)
- Type of data: Nominal or Ordinal.
- When numbers are assigned to characteristics for the purpose of data classification. Does not have a sense of order or rank.
- When numbers are
assigned to data that a sense of rank or order, but the magnitude of difference
between those numbers is not known.
- The usual central measure is a median
- Mann-Whitney test (assumes 2 independent groups (i.e., not related) being studied)
- Kruskal-Wallis test (assumes > 2 independent groups
- Spearman (correlation test)
- Gaddis ML et al. Introduction to biostatistics: part 1, basic concepts. Ann Emerg Med 1990;19:86-89.
Examples of Nonparametic Statistical Tests