Activity 15.2
Calculating a Regression Coefficient, Beta Weight, and Correlation Coefficient in SPSS

This activity will show you how to have SPSS calculate a regression coefficient, beta weight, and Pearson correlation coefficient for the regression line created in Activity 15.1. Open the "COUNTRIESdepr" data set (download / help downloading) in the SPSS data editor. Click on "Analyze" at the top of the screen; choose "Regression" from the drop-down menu and "Linear" from the next drop-down menu. A new window, titled "Linear Regression," will appear. In the "Linear Regression" window, put the variable "death" in the box marked "Dependent," and put the variable "hivaids" in box marked "Independent." Then click on the "OK" button. Output similar to that shown in Figure 15.6 will appear in the viewer.

The two important tables are the "Coefficients" and "Model Summary." Look first at the "Coefficients" table; on the left is your independent variable, percent aged 15 to 49 living with HIV/AIDS, and something called "Constant." (Constant is what is left over to explain after you have exhausted the explanatory power of your independent variable; it is the value of the Y-intercept.) For your independent variable, find the unstandardized regression coefficient, B, which in this table equals 1.487. Next find the standardized regression coefficient, Beta, for your independent variable which in this table equals 1.559.

What do the regression coefficient and beta weight tell you about the relationship between the HIV/AIDS rate and the death rate in these countries?

Return to the viewer. The other table is labeled "Model Summary." r (SPSS uses an uppercase R) is the Pearson correlation coefficient-in this case, .559, and r2 is the correlation coefficient squared, which tells you what percentage of the variance in the dependent variable you have explained-in this case, .312 or 31.2 percent.

What does the Pearson correlation coefficient and its square tell you about the relationship between the HIV/AIDS rate and the death rate in these countries?