The average, however, is not necessarily an absolute standard. We see 

 this when we consider characteristics that we can count. Thus, if we took 

 the average number of eyes in a population, we should find it to be about 

 1.995; yet the normal number of eyes is 2.0. 



When we are first impressed with the fact of "variation" we are likely 

 to assume that it is haphazard, that each individual may be "different" in 

 almost any way at all. But about a hundred years ago (1845) a Belgian 

 mathematician, after measuring and recording the dimensions of thousands 

 of people, came to the conclusion that there is a certain regularity, or order- 

 liness, in these variations. Lambert Adolphe Quetelet (1796-1874) showed 

 that variation in stature, for example, could be represented by means of a 

 simple mathematical formula (see illustration on page 69). This idea is 

 pictured also in the diagram about the line of boys of the same height (see 

 page 63). 



Normal Variation' No matter what we measure about human beings, 

 we find the same regularity. And we observe the same regularity if we 

 measure any characters of plants and animals — number of stamens in roses, 

 for example, yield of milk in cows, and so on. Every group of living things 

 consists of individuals that differ from each other: each one is "irregular" 

 or unique in his own way: Yet there is a regularity in their variations. 



United States Department of Agriculture 



AVERAGES ARE NOT ALWAYS MEANINGFUL 



It is true that the average weight of the pigs in this picture is 41.6 pounds. But that 

 tells us nothing that is characteristic of the group or of any individual. The "average" 

 figure gives no hint of the fact that the 350-pound mother weighs about 14 times 

 as much as all the little pigs together — each weighing about 3 pounds 



iSee No. 3, p. 75. 

 68 



