yi COXTENTS. 



CHAPTER III. 



THE CLASSES OF FREQUENCY POLYGONS. 



PAGE 



Classification 16 



To classify a simple frequency polygon 16 



The normal curve 18 



To compare any observed curve with the theoretical normal 



curve 19 



The index of abmodality 19 



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



observed polygon 19 



The normal curve as a binomial curve 20 



Example of a nearly normal curve 20 



Other unimodal frequency polygons . 21 



Curves of limited range 22 



Asymmetry or skewness 22 



To compare any observed frequency polygon of Type I with its 



corresponding theoretical curve 22 



To compare any observed frequency polygon of Type II with its 



corresponding theoretical curve 23 



To compare any observed frequency polygon of Type III with its 



corresponding theoretical curve 23 



To compare any observed frequency curve of Type IV with its 



corresponding theoretical curve 24 



Example of calculating the theoretical curve corresponding with ob- 

 served data 25 



Multimodal curves 26 



CHAPTER IV. 

 CORRELATED VARIABILITY. 



General principles 30 



Methods of determining coefficient of correlation 32 



Galton's graphic method 32 



Pearson's method 32 



Duncker's brief method 33 



Spurions Correlation in Indices 35 



Heredity 35 



Uniparental inheritance 36 



Biparental inheritance 36 



Galton's law of ancestral heredity 37 



CHAPTER V. 



SOME APPLICATIONS OF STATISTICAL BIOLOGICAL STUDY. 



The laws of variation.... , 38 



The causes of variation 38 



Selection 38 



The origin of species 38 



