22 



STATISTICAL METHODS. 



Value of F. 



Corresponding Frequency Curve. 



F>1 and <oo 

 ^=1 



F>0and <1 

 ^=0,ft = 0,ft=3 

 =0, ft = 0, /? 2 not 



Type III. Transitional between Type 



I and Type VI. 

 Type VI. 

 Type V. Transitional between Type 



IV and Type II. 

 Type IV. 

 Normal curve. 

 Type II. 

 Type I. 



An important relation to be referred to later is 

 M 



A 5^3210 



Fio. 5. 



THE NORMAL CURVE. 



The normal curve is symmetrical about the mode; con- 

 sequently the mode and the median and mean coincide. 

 The mathematical formula of the normal curve, a formula 



much used. jFi = 2/? 2 3ft 6. The classification was given as follows: 



/?i>0, curve is of Type I. 



Pi =0, /?2<3, curve is of Type II. 



/?i> 0, /? 2 > 3, curve is of Type III. 



ft =0, ,5 2 = 3, curve is normal. 

 When F is positive and ft > 0, 3 2 > 3, curve is of Type IV. 



When F is negative and 

 When F = Q and 



