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.

Download the file and read it into SPSS.

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.

Check suggested answer 1.

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

Check suggested answer 2.

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?

Check suggested answer 3.

4. In what units are the coefficients in the regression equation?

Check suggested answer 4.

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?

Check suggested answer 5.

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?

Check suggested answer 6.

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Last updated: 4 December, 2006.