# Rank based non parametric tests

## Objectives

On watching this video students should be able to:

- ExplainÂ why and when a non-parametric test should be used or may be preferred for simple comparison over a parametric method
- Explain the general principles and process of performing a non-parametric test based on ranks.
- Interpret the p-value from a signed ranks and Wilcoxon sum of ranks test.
- ListÂ the key strengths and weaknesses of a non-parametric test over a parametric approach.

Correction:

08:45: I say something like “ the power of a test is the ability to detect a true difference when there is a true difference”, which is a bit clumsy, you could just say “the ability to detect a true difference” or “the ability to detect a difference when there is a true difference”