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 production
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 correspondence
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 determined
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
