ABSTRACT
Medicine is an empirical science where decisions are almost invariably based on the experience gained on a sample of subjects. Since different samples contain different individuals, and individuals differ from one another, it is natural that the samples also vary from one another. For example, it is possible in a small therapeutic trial of a new regimen that six patients respond in a first sample of 10, three in a second sample, and seven in a third sample of the same size. Similarly, the mean reduction in cholesterol level in a first sample of 15 hypertensive-hypercholesterolemic subjects may be 30 mg/dL, in a second sample 24 mg/dL, and in a third sample 25 mg/dL after the same therapy. This tendency of different samples providing different results generates considerable uncertainty. One of the main objectives of statistical methods is to study these sampling fluctuations and develop strategies to draw valid conclusions for the target population on the basis of just one sample.
