Getting Started with SPSS

The Independent-Samples T Test compares the means of two independent groups to determine whether there is a significant difference between the two groups.

1. From the menu, choose Analyze > Compare Means > Independent-Samples T Test. The “Independent-Samples T Test” dialog box will appear.
2. Select one or more test variables and move the variable(s) to the Test Variable(s) list. A separate t-test is computed for each variable.

3. Select a single grouping variable and move it to the Grouping Variable field.
4. Click Define Groups to specify the two codes which identify your two groups, then click Continue (in the example, the code f was used or female and the code m for male, so we enter f in Group 1 and m in Group 2).

5. Click OK.

The output should look something like this:

The first output table Group Statistics displays descriptive statistics.

The second output table Independent Samples Test contains statistics that are critical to determine the difference between two means. The first section Levene's Test for Equality of Variances helps to determine whether you should use the statistics for equal or unequal variances

• P-value (Sig.) < significance level α indicates that the groups have unequal variances, you should use the t-test statistics in the row labeled “Equal variances not assumed”
• P-value (Sig.) > significance level α indicates that the groups have equal variances, you should use the t-test statistics in the row labeled “Equal variances assumed”

In the given example, we should look at the Equal variances assumed row (p=0.57). It can be concluded that there is no statistically significant difference in the level of income between males and females (t(6398)=0.26, p=0.980).