MACHINE OPERATORS 
II 9 
earnings of these operators, averaged over periods of from 
°ne to four months, depending on the shop and the number 
°f months of production available. In one of the three 
shops a night shift had recently started work and tests 
'Were given to twenty-one women on this shift. Many of 
these women were immigrants who could not understand 
English, and quite a number were elderly women. How 
ler, comparatively little difficulty was experienced in 
showing them how to perform the test. The results in all 
oases showed that there was a marked correspondence be 
tween ability in this test and ability to feed dial machines. 
The results in all groups may be summarized as follows: 
Correlations 
Number 
of operators 
tested 
1st trial 
2nd trial 
3rd trial 
^hst Shop. . . 
25 
■36 
.40 
•54 
Jwcond Shop.... 
22 
•43 
.14 
no trial 
Third Shop 
28 
■4i 
.28 
•43 
^bird Shop. . . . 
_ (night shift) 
21 
.22 
.22 
•50 
The correlations found are not high in every case, but 
^ the correlations obtained on the third trial are uni- 
°tmly good. This may be due to the fact that the first 
trials were too easy, whereas the third trial, with the 
°t only half open, more nearly approached the actual 
°P e ration in difficulty. It also seems likely that some 
°P e tators were so set in their regular habits of machine 
°P er ating that they could not readily adapt themselves 
^0 the changed conditions of this test. The interference 
r P r evious habits is a well-established psychological prin