A FIRST EXPERIMENT 
3 1 
could be shown, the tests would be of little worth to the 
employment office. Therefore, it was decided to take as 
the basis of each girl’s standing, an average of her work 
for four weeks. These averages were obtained by making 
a detailed statement, drawn from the separate daily pro 
duction slips of each girl, showing the number of pounds 
done for every day in the week, together with the exact 
number of hours taken to do them. The total number of 
pounds inspected by a girl, divided by the total number of 
hours worked, gave the average number of pounds per 
hour for the particular girl and became the basis for her 
ranking. In making out these statements, all work other 
than that on a single kind of shell was discarded. This 
was done for the sake of uniformity, it being manifestly 
unfair to judge the relative speed of different girls on a 
basis of pounds when one girl was inspecting large shells 
which went very quickly while another was inspecting 
small shells which went very slowly. 
After the average hourly production of each girl for a 
period of four weeks had been determined, the results were 
compared with the performance of each girl in each of the 
tests. This was done to obtain the degree of correspond 
ence or the correlation, as it is technically called, between 
the tests and the actual production. Now the method 
by which the correlation between the performance of the 
girls in the tests and their rate of production was deter 
mined was not by guesswork or by rough observation, but 
by an exact statistical process. This process is very simple 
a ud can easily be described. Let us suppose that girls 
A, B, C, D, E, F, G, H, I, and J are ten girls who have 
been tested (see table on page 32). After the tests have 
been given, it is necessary to rank them in the order of 
their ability; that is, the girl who turns out the most work