March 7, 1919] 



SCIENCE 



225 



The contrast between A and D — in- 

 telligence becomes impressive when it is 

 shown that men of A intelligence have the 

 requisite mental ability to achieve superior 

 records in college or professional school, 

 whereas D — individuals Eire rarely able 

 to pass beyond the tliird or fourth grade 

 of an elementary school, however long they 

 may attend. 



Reliability of Methods. — The methods of 

 mental examining used in the army have 

 been found to possess reliability as well as 

 practical value which far exceeded the ex- 

 pectations of the men who are responsible 

 for tliem. Indeed, the success of this par- 

 ticular methodological \indertaking is a re- 

 markable demonstration of the "fecundity 

 of aggregation." It is extremely unlikely 

 that any individual working alone would 

 have developed within reasonable time 

 equally valuable methods of group ex- 

 amining. Inasmuch as reliability is of 

 first importance, various measures of the 

 validity of the army mental tests are pre- 

 sented. 



The probable error of an Alpha score is 

 about five points. This is approximately 

 one-eighth of the standard deviation of 

 the scores for unselected soldiers. The 

 reliability coefficient of examination Alpha 

 approximates .95. This group examination 

 correlates with other measures of mental 

 ability as follows: (1) With officers' rat- 

 ings of their men, .50 to .70 for the total 

 Alpha score and .30 to .54 for the separate 

 tests; (2) with Stanford-Binet measures of 

 intelligence, .80 to .90 for the total Alpha 

 score and .31 to .85 for the separate tests; 

 (3) with the Trabue B and C Completion 

 tests combined, .72 for tlie total .score and 

 .39 to .76 for the separate tests; (4) with 

 Examination Beta, .80; (5) with the com- 

 posite result of Alpha, Beta and Stanford- 

 Binet examinations, .94; (6) in the case of 

 school children results of Alpha examina- 



tion correlate (a) with teachers' ratings 

 .f)7 to .82, (b) with school marks .50 to .60, 



(c) with school grade location of thirteen 

 and fourteen year old children .75 to .91, 



(d) with age of children .83 (for soldiers 

 the correlation of Alpha score with age is 

 practically zero). 



The Alpha examination given with 

 double the usual time allowance con-elates 

 approximately .97 with the regular time 

 examination. 



The following data indicate the reli- 

 ability of Examination Beta: It correlates 

 with Alpha. .80; with Stanford-Binet, .73; 

 with the composite of Alpha, Beta and 

 Stanford-Binet, .915. The correlation of 

 the separate Beta tests with the Stanford- 

 Binet ranges from .47 to .63 (average .58), 

 Results of Beta given with double time 

 allowance correlate with those obtained 

 with the regular time allowance .95. 



For the several forms of individual ex- 

 amination used in the army the principal 

 correlations at present available are as 

 follows : 



Results obtained by repetition of Stan- 

 ford-Binet examination of school children 

 correlate .94 to .97. Results of one half of 

 the scale compared with the otlier half 

 correlate .94 to .96. An abbreviated form 

 of the Stanford-Binet examination con- 

 sisting of two tests per year was used 

 extensively in the army. The results of 

 this abbreviated scale correlate .92 witli 

 those obtained by use of the complete scale. 



For the Point Scale examination the 

 measures of reliability are practically the 

 same as for the Stanford-Binet. 



A Performance Scale examination pre- 

 pared especially for military use consdsted 

 of ten tests. Results for the several tests 

 of the scale correlate with Stanford-Binet 

 results, .48 to .78. Five of the ten tests 

 yield a total score which correlates .84 

 with the Stanford-Binet score. The same 



