Correlation analysis

Correlation coefficients provide a numerical summary of the direction and strength of the linear relationship between two variables. The two main correlation coefficients are:

- Pearson product-moment correlation: for continuous variables, or one continuous variable and one dichotomous variable.

- Spearman rho: for ordinal level or ranked data.

The sign of the correlation coefficient indicates the direction of the correlation: a positive correlation indicates that as one variable increases, so does the other; a negative correlation indicates that as one variable increases, the other decreases. The strength of the relationship is given by the numeric value: 1 indicates a perfect relationship; 0 indicates no relationship between the variables.

Obtaining Pearson r and Spearman rho

1. Click on Analyze\Correlate\Bivariate.
2. Select your two variables and move them into the box Variables.
3. In the Correlation Coefficients section, Pearson is the default option. If you wish to request the Spearman rho, tick the Spearman box as well (or instead).
4. Under Options, click on the Exclude cases pairwise box.
5. Click on Continue, then OK.