32 STATISTICAL METHODS. 



To find 1 19 1 2 , m l9 m 2 , y Q . 



The total range, /, of the curve (along the abscissa axis) 

 is found by the equation 



/ t and 1 2 are the ranges to the one side and the other of jfo; 



1 =(s 2); m 1 + m 2 =5 2; 



To solve this equation it will be necessary to determine 

 the value of each parenthetical quantity following the F 

 sign and find the corresponding value of F from Table V. 

 It is, however, sometimes easier to calculate the value of y Q 

 from the following approximate formula: 



_n 

 2/o 



I ' 



With these data the theoretical curve of Type I maybe 

 drawn. Frequency polygons of Type I are often found in 

 biological measurements. 



To compare any observed frequency polygon 

 of Type II with its corresponding theoretical 

 curve, 



y == 2/0 \ * 172 



\ > 



This equation is only a special form of the equation of Type 

 I in which Z 1 = Z 2 and m 1 = m 2 . 



As from page 22, ^ = in Type II, Z=2cr\/s+l; since the 

 curve is symmetrical, Z) = 0, and 



if _ov _n r(m+1.5) 



yVfriXm+l)' 



The F values will be found from Table V. 



