Final answer:
R-squared is used in two-way between-groups ANOVA to measure effect size for three effects: each independent variable and their interaction. The correct answer is c) R2; three.
Step-by-step explanation:
When performing a two-way between-groups ANOVA, effect size is measured using R-squared (R2), and it is calculated for three different effects: the effect of each of the two independent variables and the interaction effect between them.
Unlike Cohen's d, which is used for measuring effect size between two means, R2 represents the proportion of variance accounted for by the independent variables in the model. For example, a larger R2 value indicates a more substantial effect of the independent variables on the dependent variable.
Effect size is a measure of the magnitude of the differences between groups. In a two-way between-groups ANOVA, there are three effects: the main effect of factor A, the main effect of factor B, and the interaction effect between factor A and B.
R2, also known as the coefficient of determination, is a commonly used measure of effect size that ranges from 0 to 1, indicating the proportion of variance in the dependent variable that is explained by the independent variables.