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LABORATORY GUIDE IN PHYSIOLOGY. 



the whole result. If there aie 100 or 1000 individ- 

 uals in a group, then the use of the old method of finding 

 the arithmetrical average is exceedingly wasteful of both 

 time and energy. It must be added, however, that when 

 the number of observations is large the chances are that 

 there will be as many dwarfs as giants, thus making the 

 average approximate closely the median value. It is the 

 latter that we are seeking, viz. : the median value; this 

 may be defined as that value which is so located in 

 the whole series of observations, in a single measurement 

 of any group, that there are as many below it as above it, 

 i. e., that fhe numbers of values which it exceeds is equal 

 to the number of values which exceed it. 



Let us take a concrete case. In a group of 316 seven- 

 teen-year old boys certain physical measurements were 

 recorded upon individual cards. Let us take for an ex- 

 ample thegirihof head recorded in centimeters and tenths. 

 Instead of writing in a column the 316 head girths, each 

 expressed in three figures, adding and averaging, let us 

 adopt the new method first suggested by the Belgian as- 

 tronomer and anthropologist, Quitelet, and later elabo- 

 rated by Galton, the London anthropologist.* Arrange 

 the cards in piles, placing in one pile all of the cards 

 having girth of head 51+ centimeters, in another pile all 

 having 52-[- centimeters, and so on. In the case in ques- 

 tion it was found that the 316 cards were quickly distrib- 

 uted, falling into the following groups: 



*For a more extended explanation and development of this method 

 than given in this chapter see also " Changes in the Proportions of the 

 Human Body" Hall. Journal of the Anthi opological Institute of Great 

 Britain and Ireland. London, AugUbt, 1895. 



