EXPLANATION OF TABLES. 



115 



INDEX TO THE PRINCIPAL LETTERS USED IN THE 

 FORMULA OF THIS BOOK. 



A, average, mean, 

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

 left-hand quadrant (p. 49). 



a, skewness index. 



b, 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). 



J, index of closeness of fit. 

 8, difference between y and /. 



E, pfobable error. 



e, base of Naperian logarithms, 

 = 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 



p"th individual, 

 i, 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. 

 I, range of curve along x. 

 li, lz, portions of the curve range. 

 A , number of classes. 

 A, class range. 

 M, abscissal value of the mode 



(theoretical). 

 M r , abscissal value of the mode 



(empirical). 

 /t, moment about A. 

 N, the number corresponding to 



a log. 



n, number of variates; area of 

 polygon; any, not specified, 

 number. 



\n, .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. 



TT, circumference in units of diame- 

 ter, 2.14159. 



q, a root or power. 



r, coefficient of correlation. 



P, coefficient of regression. 



s, a relation of /?'s (p. 22). 



I, summation sign. 



a, standard deviation; index of 

 variability. 



T, transmuting factor, a into E, 

 .67449. 



T, in Type IV. 



' j- angles. 

 <f>, ) 



V, magnitude of any class. 



V , magnitude of central class. 



v, any variate or value. 



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



X, the horizontal axis or base of 



polygon. 



.x, a varying abscissal value. 

 x\, x 2 , etc., definite values of x. 



Y, the vertical axis of polygons* 

 also the log of / (p. 29). 



y, a varying ordinate value. 



yo, value of the ordinate at the 

 origin. 



z, ordinate value. 



