EXPLANATION OF TABLES. 



115 



INDEX TO THE PRINCIPAL LETTERS USED IN THE 

 FORMULAE OF THIS BOOK. 



A, average, mean. 



a, class index (p. 24); also upper 



left-hand quadrant (p. 49). 

 a, skewness index. 



6, the frequency of the upper 

 right quadrant (p. 49). 



/?, ratio of moments. 



C, coefficient of variability. 



c, the frequency of the lower left 

 quadrant (p. 49). 



D, distance from mean to mode. 



d, a difference; differential; the 

 frequency of lower right quad- 

 rant (p. 49). 



4, index of closeness of fit. 



d, difference between y and /. 



E, probable error. 



e, base of Naperian logarithms, 

 1 =2.718282. 



F, critical function. 

 /, class frequency. 



G, geometric mean. 

 H, a function of h. 



h, a fixed value of x\ also, index of 

 heredity. 



7, interval between the p'th and 

 j>"th individual. 



t, interval between the pth and 



(p + l)th individual (p. 27). 

 K, a function of k. 

 k, a fixed value of x. 

 L, limiting value of class. 

 Z, range of curve along x. 

 l\, ^2, portions of the curve range. 

 A , number of classes. 

 A, class range. 

 M , abscissal value of the mode 



(theoretical). 

 M', abscissal value of the mode 



(empirical). 

 H, moment about A. 

 N, the number corresponding to 



a log. 



n, number of variates; area of 



polygon; any, not specified, 



number. 

 |rc_, product of all integers from 



1 to n. 



v, average moment about VQ. 

 H, index of dissymmetry. 

 P, probability 

 p, ordinal rank of a particular 



individual or case (p. 27); a 



root or power. 

 ic, circumference in units of diame- 



ter, 3.14159. 

 q, a root or power. 

 r, coefficient of correlation. 

 p, coefficient of regression. 

 s, a relation of @'s (p. 22). 

 2", summation sign. 

 <?, standard deviation; index of 



variability. 

 T, transmuting factor, o into E, 



.67449. 

 r, in Type IV. 



' f angles. 



9 ) 



V, magnitude of any class. 



FO, magnitude of central class. 



v, any variate or value. 



= 5/? 2 -6/?i-9 (p. 31). 



X, the horizontal axis or base of 



polygon. 



x, a varying abscissal value. 

 x\, X2, etc., definite values of x. 



Y, the vertical axis of polygons ; 



also the log of / (p. 29). 

 y, a varying ordinate value. 

 2/0, value of the ordinate at the 



origin. 

 z, ordinate value. 



