AY 
PREDICTION OF VOCATIONAL SUCCESS 
Prediction based on group comparison. Critical scores and critical sections. 
THE two foregoing chapters dealt with the determination 
of the relationship between measurements and the criterion 
of vocational accomplishment. When significant relation- 
ships have been discovered either by inspection or by the 
statistical methods there described, the relative value of par- 
ticular scores in forecasting vocational success must be de- 
termined before practical use can be made of these findings. 
Two general types of procedure are available, one based on 
the study of group differences, the other on the establish- 
ment of correlation between measurements. 
PREDICTION BASED ON GROUP COMPARISON 
The groups to be compared are made up of the successful 
and the unsuccessful employees; or those who remain with 
the company and those who leave; those who learn quickly 
and those who take a longer time to acquire the necessary 
vocational skill; those who earn a promotion and those who 
do not; those who have few accidents and those who have 
many; those who sell more than their quota and those who 
sell less, and so forth. When two or more groups represent- 
ing different levels of vocational accomplishment are to be 
compared in terms of test scores, practical procedure de- 
mands a way of determining the score or scores which best 
differentiate the group or groups. 
A test score above which or below which the members of 
one group are represented in conspicuously greater propor- 
tion than the members of the other group, is called a critical 
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