A physician compared the cholesterol levels of a representative sample of Americans who ate an American diet vs. a representative sample of those who followed a Mediterranean diet. Below are the means, standard deviations, and sample sizes for both samples.

Though in some studies a Mediterranean diet has been shown to be beneficial, this was one of the first studies on an American population and the physician had made no advance predictions about the outcome.

• American diet (control): M = 230, s = 24, n = 36

• Mediterranean (experimental): M = 190, s = 26, n = 36