Analysis of variance (ANOVA) is one of the most frequently used techniques in the biological and environmental sciences. ANOVA is used to contrast a continuous dependent variable *y* across levels of one or more categorical independent variables *x*. The independent variables are termed the factor or treatment, and the various categories within that treatment are termed the levels. In this module, we will start with the simplest design - those with a single factor.

Where an independent samples *t*-test would be used for comparison of group means across two levels, ANOVA is used for the comparison of >2 group means, or when there are more than two or more predictor variables (see ANOVA: factorial). The logic of this test is essentially the same as the *t*-test - it compares variation between groups to variation within groups to determine whether the observed differences are due to chance or not.