VI CONTENTS. 



PAGE 



Coefficient of variability 16 



The probable error of the coefficient of variability 16 



Quick methods of roughly determining average and variability ... 17 



CHAPTER III. 

 THE CLASSES OF FREQUENCY POLYGONS. 



Classification 19 



To classify a simple frequency polygon 19 



The normal curve 22 



To compare any observed curve with the theoretical normal 



curve 23 



The index of abmodality 23 



To determine the closeness of fit of a theoretical polygon to the 



observed polygon 24 



To determine the probability of a given distribution being 



normal 24 



The probable range of abscissae 25 



The normal curve as a binomial curve 25 



Example of a normal curve 26 



To find the average difference between the pth and the (p-fl)th 



individual in any seriation 27 



To find the best fitting normal frequency distribution when only a 



portion of an empirical distribution is given 28 



Other unimodal frequency polygons 30 



The range of the curve 30 



Asymmetry or skewness 30 



To compare any observed frequency polygon of Type I with its 



corresponding theoretical curve 31 



To compare any observed frequency polygon of Type II with 



its corresponding theoretical curve 32 



To compare any observed frequency polygon of Type III with 



its corresponding theoretical curve 33 



To compare any observed frequency curve of Type IV with its 



corresponding theoretical curve 33 



To compare any observed frequency polygon of Type V with 



its corresponding theoretical curve 34 



To compare any observed frequency polygon of Type VI with 



its corresponding theoretical curve 34 



Example of calculating the theoretical curve corresponding with 



observed data 35 



The use of logarithms in curve fitting 36 



General 38 



Type IV 39 



Multimodal curves 39 



CHAPTER IV. 

 CORRELATED VARIABILITY. 



General principles . . . . 42 



Methods of determining coefficient of correlation 44 



