Which statement about fixed effect is true?

Which statement about fixed effect is true?

• A. It is generalized only to the situations in the experiment
• B. It generalizes to the entire population
• C. It cannot be fixed
• D. It always involves random intercepts

Answer: (A)

Fixed effects refer to the impacts of factor levels that are the specific ones you included in your study. Because you’re estimating the differences among those exact levels, the conclusions you draw apply only to those particular conditions and to the population of units observed under those conditions. They aren’t intended to generalize to all possible conditions or to a broader population beyond what was tested. That’s why the statement that fixed effects generalize only to the situations in the experiment is the correct one. Other statements don’t fit this idea. Fixed effects are called fixed because the levels are fixed, not random draws, so saying it cannot be fixed is inaccurate. Random intercepts are a feature of models with random effects; a fixed-effects framework doesn’t require random intercepts. Inference from fixed effects isn’t intended to generalize to an entire population of conditions, only to the specific conditions studied.

Fixed effects refer to the impacts of factor levels that are the specific ones you included in your study. Because you’re estimating the differences among those exact levels, the conclusions you draw apply only to those particular conditions and to the population of units observed under those conditions. They aren’t intended to generalize to all possible conditions or to a broader population beyond what was tested. That’s why the statement that fixed effects generalize only to the situations in the experiment is the correct one.

Other statements don’t fit this idea. Fixed effects are called fixed because the levels are fixed, not random draws, so saying it cannot be fixed is inaccurate. Random intercepts are a feature of models with random effects; a fixed-effects framework doesn’t require random intercepts. Inference from fixed effects isn’t intended to generalize to an entire population of conditions, only to the specific conditions studied.