The terms "norm" and "normal" generally refer to what is customary or usual, or sometimes to what is desirable. In a technical sense, "norm" applies to standards or criteria, and may be applied to either a measurable variable, such as height or weight, or to a way of behaving. In medicine and in public health, "normal" has several meanings: it can mean healthy, or in a more precise sense it may mean that the value of a variable such as temperature or blood pressure is within generally accepted limits applicable to healthy people. In statistics, a normal distribution is defined as a continuous frequency distribution of infinite range in which values are symmetrically distributed about a central mean.
JOHN M. LAST