VALIDATION OF MEASURING INSTRUMENTS 16 5 
steps that may be required in treatment of data, reminding 
the investigator of essential procedures while referring him 
to the authorities for more detailed directions, as well as for 
complete expositions of the statistical theory underlying the 
formulas recommended. 
Tabulation. Several points are to be kept in mind in plan- 
ning the tabulation of the data which have been gathered. 
The tabulation should put the figures in shape for rapid and 
convenient statistical treatment and for ease in locating any 
individual’s record. Rugg describes various ways in which 
this may be done (157, ch. iii). If there are as many as 20 
measures on 1,000 subjects, it will be advisable to resort to 
a mechanical tabulating device such as the Powers or the 
Hollerith machine. 
In tabulating, the investigator should not fail to make use 
of additional scores which the test may yield, since each new 
set of scores derived from a different aspect of a test is the 
equivalent of another test. An illustration of this is found in 
a study by Manson (106), in which it was discovered that in 
discriminating between two groups of students the score in 
an intelligence test was less important than the number of 
items skipped, a measure which had hitherto been neglected. 
If the investigator is working with applicants rather than 
with old employees, it will be necessary to lay the tabulated 
data aside until reliable figures on the vocational success of 
the men are at hand. It is sometimes advisable to place in 
the hands of an executive a duplicate set of the scores. They 
should be in a sealed envelope so that they will not affect his 
judgments before the time arrives for a comparison of these 
data with the records of accomplishment. 
Reliability. Before proceeding to the presentation of 
methods of determining the validity of the measuring instru- 
ments, it is necessary to give some attention to an important 
step, the determination of the reliability of the measures. 
The validity of a test is its relationship with the criterion, 
that is, the proportion of commonality of abilities measured