The Effects of Polyunsaturated Fat vs Monounsaturated Fat on Plasma Lipoproteins: The Power of a Study

To the Editor.—  It is amazing that despite all the attempts over the past few years to increase the appropriate use of statistics in the general medical literature, you have once again published an interventional trial with negative results with no discussion whatever of the power of the study to detect a difference in the study groups.¹The following statement by Dreon et al¹ is simply false: "The present results in free-living men and women demonstrated that exchanging unsaturated fats within current guidelines in reduced- fat diets does not affect plasma total cholesterol or LDL [low-density lipoprotein] cholesterol levels." What is true is that the study failed to demonstrate an effect of exchanging unsaturated fats, but the authors do not discuss what the chance is that this was simply because the study groups were too small. I grant you that they did make one insufficient allusion to wide