When results show a difference between levels of a factor,this difference is called ______.

A) an interaction effect
B) a factor effect
C) a level effect
D) a main effect

A main effect is defined as the effect of one independent variable on a dependent variable while ignoring the effects of other independent variables. When there is a difference between levels of a factor, it is known as a main effect, indicating that the factor played a significant role in influencing the dependent variable. An interaction effect occurs when the effect of one independent variable on the dependent variable differs depending on the level of another independent variable, and a level effect is not a statistical term.