EMPLOYMENT PSYCHOLOGY 
who are high, average, and low in the ability in question. 
Then he takes each group in turn and ranks the men in it. 
By assembling his groups of cards in proper order he com- 
pletes his ranking. 
The order-of-merit method makes distinctions in ability 
which are finer than necessary or even possible if the group 
is large. It gives the rater no framework on which to hang 
his judgments. Moreover, unless statistical corrections are 
made, it assumes that a unit difference in rank always indi- 
cates a constant difference in abilities, whereas this differ- 
ence is greater at the extremes of ability than in the middle 
range. If 50 men are ranked in any ability, the difference 
in ability between the first and second man is greater than 
the difference between the twenty-fourth and twenty-fifth 
man. In spite of these disadvantages the order-of-merit 
method is one of the best known, since it gets at the heart 
of the matter by disregarding all other persons or impres- 
sions and simply requiring comparisons between the mem- 
bers of the group under consideration. 
Grouping. The judge places the subjects in three groups, 
consisting of those who excel in the ability, those who are 
undistinguished in the ability, and those who fall below 
in the ability. The judge may or may not be instructed to 
make the groups equal in size. The number of groups may 
be increased at the discretion of the investigator. Symonds 
contends that seven is the optimum number of groups, 
although he has not proved his point experimentally (179). 
Ratings of several judges may easily be combined if a nu- 
merical value is assigned to each of the groups. 
The Scott form of man-to-man comparison scale. This 
is the rating method originally developed at Carnegie In- 
stitute of Technology for the selection of salesmen, and later 
adapted for use in rating officers in the United States Army 
during the World War (137). The judge makes a master 
scale for each ability by the following process: He selects 
the highest and the lowest man in the ability in the group 
124A