By Student 
25 
Section X. 
Coiiclusiunii: 
I. A curve has been found representing the frequency distribution of standard 
deviations of samples drawn from a normal population. 
II. A curve has been found representing the frequency distribution of values 
of the means of such samples, when these values are measured from the mean of 
the population in terms of the standard deviation of the sample. 
III. It has been shown that this curve represents the facts faii'ly well even 
when the distribution of the population is not strictly normal. 
IV. Tables are given by which it can be judged whether a series of experiments, 
however short, have given a result which conforms to any required standard of 
accuracy or whether it is necessary to continue the investigation. 
Finally I should like to express my thanks to Professor Karl Pearson, without 
whose constant advice and criticism this paper could not have been written. 
Biometrika vi 
4 
