Independent Means
When there is no subject overlap across groups, we define the groups as independent. Tests of gender differences are a good example of independent groups. We cannot be both male and female at the same time; the groups are completely independent. If you want to determine whether samples are independent or not, ask yourself, "Can a person be in one group at the same time he or she is in another?" If the answer is no (can't be in a remedial education program and a regular classroom at the same time; can't be a freshman in high school and a sophomore in high school at the same time), then the groups are independent.

The statistics that can be used for independent groups include the chi-square test of independence (two or more groups), Mann-Whitney U Test (two groups), Independent Means t test (two groups), One-Way Between-Groups ANOVA (three or more groups), and Factorial ANOVA (two or more independent variables).