288 



MISCELLANEOUS STUDIES 



If the probable error of the difference of any two percentages in 

 the same table is to be obtained, therefore, formulae corresponding to 

 those given by Yule (1911, pp. 264-267) are applicable. 



Now, it is possible in some of these cases to calculate the actual 

 standard deviation of the percentage in subsamples which make up 

 an aggregate sample. Table 39 gives such actual standard deviations, 

 in comparison with the corresponding theoretical or expected standard 

 deviations given by , 



_ y pq 



" per cent I 



n 3 



TABLE 39 



Standard deviations of percentages of mutant types. Values derived from V pq, 

 compared with values expressing the actual variability of subsamples. 



"The second values for some cases in this column are derived from p a (see text). 



[1461 



