Related Procedures

The independent-samples t test is appropriate whenever two means drawn from independent samples are to be compared. The variable used to form the groups may already exist; however, a cut point on a continuous variable can be provided to dynamically create the groups during the analysis. As with all t tests, the independent-samples t test assumes that each sample mean comes from a population that is reasonably normally distributed, especially with respect to skewness. Test variables with extreme or outlying values should be carefully checked; boxplots can be used for this.

There are other procedures which you can use to test the assumption of normality. See the topic Exploratory Data Analysis for more information.
If your grouping variable has more than two groups, try the One-Way ANOVA procedure.