There are several different types of effects in a research study, including main effects, interaction effects, and mediator or moderator effects. - Main effects refer to the direct impact of one variable on another variable. For example, a study might investigate the main effect of a new medication on reducing symptoms of depression. - Interaction effects occur when the effect of one variable on an outcome depends on the level of another variable. This is also known as a moderating effect, as one variable moderates the relationship between the other variables. For example, a study might find that the effect of a new educational intervention on test scores varies depending on the students' prior knowledge. - Mediator effects occur when the relationship between two variables is explained by a third variable. In other words, the third variable acts as a mediator between the independent and dependent variables. For example, a study might find that the relationship between exercise and weight loss is mediated by changes in metabolism. - Moderator effects occur when the relationship between two variables is influenced by a third variable. This is often confused with interaction effects, but in this case, the moderator variable affects the strength or direction of the relationship between the independent and dependent variables, rather than the relationship itself. For example, a study might find that the relationship between stress and job performance is moderated by the level of social support in the workplace.