In Brief 



Each individual differs from other members of his group in physical 

 characteristics, in chemical make-up, and in many organic capacities. 



Each person builds up his own picture of what is normal, or standard, 

 with respect to the numerous details of life. 



A common way of finding norms for groups is to determine the average 

 for each of several sets of measurements. 



The individuality of any living thing lies in its unique combination of 

 many varying factors. 



Although each individual is unique, several unique things resemble each 

 other sufficiently to let us deal with them as of the "same" species or kind. 



Each person apparently wishes to be like others of his group, yet distinct 

 enough to be recognized as an individual. 



Standardized ways of doing things under different circumstances repre- 

 sent the price we pay for the satisfactions and benefits we derive from liv- 

 ing with others. 



EXPLORATIONS AND PROJECTS 



1 To find the variations among the individuals of a group, note the ways in 

 which the various members of the class differ from one another. List the kinds of 

 variations found. Do the same for the individuals in a litter of mammals, or a 

 brood of chicks, or the leaves from a given tree, or some other group of "the 

 same kind". 



2 To find the extent to which the members of a group vary in stature: 

 Line members up in order of height and note (a) the region in which there 



are the greatest numbers having almost the same height; {h) the relative numbers 

 of very tall, of very short, and of medium height. 



To find the middle height, or median height, of the group, count from either 

 end, to locate the middle person. The height of this person (or the average height 

 of the two at the middle, if the group happens to be even-numbered) is the 

 ■median. This measurement is also called the 50-percentile, as half the group are 

 taller and half are shorter. By counting individuals either way from the median, 

 pick out the persons whose heights may be considered 25-percentile and the 

 75-percentile. Those taller than the 75-percentile are considered in the upper 

 quartile, and those shorter than the 25-percentile are considered in the lower quar- 

 tile, so far as height is concerned. Compare the median with the calculated 

 average for the group. 



To find the range of variation, determine the difference between the shortest 

 and tallest members, or the total variation in height of the class. Find how the 

 range of the lower half compares with that of the upper half. Find how the 

 range of each of the four quarters compares with that of the others. 



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