28 LABORATORY MANUAL OF ANTHROPOMETRY 



The top ends of the columns mark the position of the Frequency 

 Curve which may be easily drawn. 



As used in anthropometry frequency curves are most usually drawn 

 upon a basis of groups of numbers, instead of using each consecutive 

 one, 10 or 5 being convenient numbers to use in grouping. Thus the 

 results of the measurement of the length of the radius in 100 students 

 (females) were the following, grouped into groups each of five milli- 

 meters extent: 



Extent in millimeters of each group Frequency; i.e., number of individuals within each 



group 



210-215 1 



215-220 1 



220-225 5 

 225-230 . . 11 



230-235 12 



235-240 12 



240-245 16 



245-250 8 



250-255 9 



255-260 7 



260-265 5 



265-270 4 



270-275 1 



275-280 2 



280-285 4 



285-290 2 



100 



A frequency curve may be easily made from the above by erecting 16 

 columns, of which the first and second have a height of 1, the third one 

 of 5, the fourth one of 11, and so on, the crest, which indicates in a general 

 way the average of all, falling at the top of the seventh column, which is 

 16 units high. Where, as in this case, a short column intervenes between 

 two taller ones, as at the thirteenth column, which is 1, followed by 

 higher ones, it is an indication that the groups of units are too small, 

 and tend to make a jagged frequency curve. In such a case the curve 

 may be smoothed out by combining the groups into larger ones. If, for 

 example, we combined these groups in pairs and had an interval of ten, 

 instead of five, for each, we would avoid any such intermediate short 

 columns, thus: 



Groups, with 10-millimeter intervals Frequency (individuals in each group) 



210-220 2 



220-230 16 



230-240 24 



240-250 24 



250-260 16 



260-270 9 



270-280 3 



280-290 6 



