# Exercise: Muscle strength, age and height for alcoholic men

The file strength.sav contains the quadriceps muscle strength data for alcoholic men analysed in the lecture for Week 9.

In this exercise we shall analyse the measurements of quadriceps muscle strength, height and age.

## Questions

1. Draw scatter diagrams for strength against height and against age and for height against age.

2. Calculate correlation coefficients between strength, height, and age. Report the correlation coefficients to two decimal places. What do these correlation coefficients tell us?

3. Calculate the linear regression of strength on height. Report the regression equation to a suitable number of decimal places. How does the result of the significance test of the slope of this line differ from the test for the correlation of strength and height?

5. Plot a histogram and Normal plot for the residuals. (To do this you need to click Plots in the regression screen.) Do the residuals appear to follow a Normal distribution?

6. Plot the residuals against height. (To do this you will have to save the residuals in the regression screen.) Does there appear to be any non-linearity?