Non-parametric inferential statistics

Inferential statistics suggest statements or make predictions about a population based on a sample from that population. Non-parametric tests relate to data that are flexible and do not follow a normal distribution.

They are also known as “distribution-free” and the data are generally ranked or grouped.  Non-parametric data are lacking those same parameters and cannot be added, subtracted, multiplied, or divided. These data include nominal measurements such as gender or race; or ordinal levels of measurement such as IQ scales, or survey response categories such as “good, better, best”, “agree, neutral, disagree”, etc.

Examples of non-parametric inferential tests include ranking, the chi-square test, binomial test and Spearman's rank correlation coefficient.


Price, J., & Chamberlayne, D. W. (2008). Descriptive and Multivariate Statistics. IACA. (PDF, 124KB)

Woolf, L. M. (n.d.). Introduction to measurement and statistics. Retrieved from

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