Activity 17.3
Using SPSS to Compare Two Means with a t-test

Go to SPSS and open the 2000 National Election Studies data set (NES2000depr) that accompanies this text (download / help downloading). You are going to test the hypothesis that younger people are more likely to do volunteer work than older people by comparing the mean ages of those who say they do volunteer work with those who say they do not. Click on "Analyze" near the top of the page; when a box appears under "Analyze," click on "Compare Means"; when a box appears to the side, click on "Independent Samples T-test." You are now looking at a new window titled, "Independent Samples T-test." Scroll through the variables on the left and highlight "age." Use the arrow button to move "age" into the box titled "Test Variable(s)." Next use the arrow button to move the variable "voluntwk" into the box titled "Grouping Variable." Below this box is a button labeled "Define Groups," which allows you to tell SPSS which two groups you want to compare. After clicking on this button, you will be prompted to fill in the appropriate variable values for "voluntwk." In the data set, the variable "voluntwk" has two values: yes and no. Yes has been given the value label 1, and No is 5. Consequently, enter the value 1 for Group 1 and 5 for Group 2. Click on the "Continue" button, then on the "OK" button. SPSS will calculate the mean age for those who volunteered and those who did not, a t score for those two means, and the level of statistical significance. Describe the difference between the mean age of those who do volunteer work and those who do not. Explain how likely is it that there is no difference between these mean ages in the population from which this sample was drawn.