22.1 Correlation Coefficient

Consider the measures from the height (in inches) and weight (in pounds) of the 92 students whose data are included in the file PULSE.MTW.

Before starting to calculate the correlation coefficient, it is highly recommended to construct a scatterplot of the data to identify possible outliers, nonlinear relationships (correlation coefficient only measures linear relationships), etc.

Graph > Scatterplot: Simple

nc22uf001.eps

To calculate the correlation coefficient, do the following.

Stat > Basic Statistics > Correlation

nc22uf002.eps

In this way, the output in the session window looks as follows:

nc22uf003.eps
The statistical significance of a correlation coefficient depends not only on its value, but also on the size of the samples used for its calculation. Do not compare directly correlation coefficients obtained from data sets of different size, but through the p-value.

You can also select more than two variables, in which case pairwise correlation coefficients are calculated. ...

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