Assessing Which Statistical Test to Choose:

1.) What kind of data do I have?

Nominal level (non-parametric): category data e.g. yes/no

Ordinal level(non-parametric): data that is a score or ranked e.g. 1st 2nd

Interval data (parametric)– standard unit of measurement e.g. seconds, KG

Criteria of parametric data

  1. interval data – it’s a standard unit of measurement
  2. population has a normal distribution
  3. homogeneity of variance – set of scores in each condition have similar dispersion

2.) A correlation or experimental difference?

Difference between behaviours in 2+ conditions e.g. experiments or research into relationships between to 2 covariables e.g. correlation

3.) What is the experimental design

If it is an experiment, the experimental design affects the statistical test chosen

Independent groups or non-independent groups (repeated measures/matched pairs)

Types of Statistical tests

Nature of Hypothesis Level of measurement Experimental design
    Independent Not independent
Test of Difference


Nominal Chi squared test Sign test
Ordinal Mann-Whitney Wilcoxon Test
Interval (parametric) Unrelated T test Related T test


Types of Statistical tests



Ordinal Spearmans Rho
Interval Pearsons R test