# Survey research and design in psychology/Tutorials/ANOVA/Effect size

## Effect size

View the accompanying screencast: [1] |

ANOVAs in SPSS can provide the partial eta-square ( ; although its labelled as eta-square). (which is equivalent of *R*^{2} in MLR) needs to be calculated manually from the output. This will help to explain the overall effects.

If you wish to discuss the size of effects between two means, then Cohen's *d* for each pairwise contrast of interest should be provided.

Calculate and interpret all effect sizes that can enhance understanding of the data in relation to the hypothesis or research question.

- Eta-square
- Percentage of variance explained by one or more IVs

- Eta-square: Calculation of overall needs to be done manually.
- Partial eta-square: Calculation is via PASW Analyze - (Type) - Options - Effect size

- Cohen's
*d* - Standardised mean difference between two means

- Cohen's d: Calculate using a spreadsheet calculator
- Cohen's d.xls

- See also