Choosing a statistical test

Statistical tests

Used in psychology to determine whether a significant difference or correlation exists.

Sign test

A test for difference between 2 sets of scores.

Data should be at least nominal and the experimental design is related.

Chi-squared

A test for association between 2 variables or conditions.

Data should be at least nominal and the experimental design is unrelated

Wilcoxon

A test for difference between 2 sets of scores.

Data should be at least ordinal and the experimental design is related

Mann-Whitney

A test for difference between 2 sets of scores.

Data should be at least ordinal and the experimental design is unrelated.

Spearman’s rho

A test for correlation when data is at least ordinal level

Pearson’s r

A parametric test for a correlation when data is at interval level.

Related t-test

A parametric test for difference between 2 sets of scores.

Data should be at least interval and the experimental design is related.

Unrelated t-test

A parametric test for difference between 2 sets of scores.

Data should be at least interval and the experimental design is unrelated.

Level of measurement

Quantitative data can be classified into types or level of measurement such as nominal, ordinal and interval

Nominal data

Data that is in separate categories

Ordinal data

Data that is ordered in some way but the intervals between each item are unequal

Interval data

Data that is measured on a scale where the distance between each value is the same, such as when counting correct answers.

Experimental design

The different ways in which participants can be organised in relation to the experimental conditions

Related experimental designs

Repeated measures

Matched pairs

Unrelated experimental designs

Independent groups