858 



MEMOIRS NATIONAL ACADEMY OF SCIENCES, 



[Vol. XV, 



The irregularity in the ratings of the officers is due, it appears, to the inclusion of the 

 medical officers with the others. Officers of the Medical Department grade lower than 

 the officers of any other branch of the service (v. infra). There are no second lieutenants in 

 either the Medical Corps or the Dental Corps, and this fact caused the percentage of high 

 grades to be greater among the second lieutenants and less among the first lieutenants than 

 would otherwise have been the case. Of the first lieutenants and captains used in this study 

 more than one- third are from the Medical Department; these two ranks rate low. In view of 

 these facts table 407 has been prepared in which ratings of medical officers are omitted, 

 figure 60 presents the facts shown in table 407, together with the data concerning the enlisted 

 men; figure 61 and table 40S present the same data for the officers of the Medical Department. 



Table 407. — Percentages of intelligence ratings by rank of white officers except officers in Medical Department. 



11,100 CASES. 



Table 408. — Percentages of intelligence ratings by ranis of while officers in the Medical Department only. 



3,955 CASES. 



The mean alpha scores for the various ranks (exclusive of the medical officers), together 

 with the probable errors, are shown in table 409, while in table 410 are presented the ratios of 

 the differences between means to the probable errors of the differences. These ratios indicate 

 that the differences are mathematically significant (the chances of the difference being reversed 

 varies from 75 per cent to 0.1 per cent; in 3 cases out of 10 it is less than 33 per cent) ; the abso- 

 lute size of the difference (maximal 5.4 points), however, is not of psychological significance. 

 There is no assurance that a significant difference of five points or less on the scale of alpha 

 represents a psychological fact and not an artifact. Thus it appears that there are at 

 most only slight differences according to rank among the officers outside the Medical Department. 

 The captains fall a little below the first and second lieutenants, but the differences are hardly 

 significant. On the whole it seems safe to say that among the officers outside the Medical 

 Department intelligence differences according to rank were, at the time and under conditions of 

 the testing, of no psychological significance. The percentages of A and B grades from table 407 

 support this conclusion. 



Among the officers of the Medical Department the situation is quite different. Table 408 

 and figure 61 show a considerable agreement between rank and intelligence rating. A notice- 

 able fact, when one considers, for example, the percentage of A and B grades, is that there is 

 little difference between the first lieutenants and the captains, but that there is a relatively 



