Wilcoxon Rank Sum test

Question 1

What is an alternative name for the Wilcoxon test?

Answer 1

Man-Whitney U test

etc.

Question 2

What are the assumptions of a Wilcoxon test?

Answer 2

1) Data is non-normally distributed
2) continuous data
3) between two groups
4) data points are independent (different groups)

Question 3

What is the null hypothesis for a Wilcoxon test?

Answer 3

If we select one value at random from each group, the value from the first group will be larger than the value from the second group 50% of the time (i.e. there is an even chance of each group obtaining the greater value)

Question 4

What is the aim of a Wilcoxon test?

Answer 4

A test of whether one group has larger values on average than another

Question 5

When can the Wilcoxon test be used to see if the median is different between groups?

Answer 5

If each group has the same distribution shape

Question 6

What is the difference between parametric and non parametric tests?

Answer 6

Parametric test: considers the form of data (a parameter)-more powerful
Non-parametric test: does not consider the form of data-less powerful

Question 7

Why is Wilcoxon a non-parametric test?

Answer 7

It does not consider the form of data as it uses a non-normally distribution

Question 8

what are some alternative tests to use for paired data and data involving 2+ groups?

Answer 8

paired data (one group repeated): Wilcoxon signed rank
2+: kruskal Wallis test