PSYCHOLOGICAL MEASUREMENTS. 573 



is given, some subjects will have a column only partly added. Ob- 

 viously they can not be allowed to complete the column. The possi- 

 bility of having the subject draw a mark through the column and 

 write down the sum to that point, was considered. It seemed, how- 

 ever, that this would introduce the possibility of much irregularity 

 and that as the time limit allowed for the task was 10 full minutes 

 without interruption, it would be better to sacrifice this fraction of 

 achievement in favor of a more simple and concise method of pro- 

 cedure. On the average, over 50 columns were correctly added dur- 

 ing the 10-minute interval. The average loss could thus be not more 

 than 2 per cent. 



In the oft-repeated instructions, which always preceded the addi- 

 tion experiment, the matter of accuracy was given much more promi- 

 nence than speed. The men were made to understand definitely that 

 a column added incorrectly had better not have been added at all, so 

 far as the score of the subject was concerned. In tables 155 and 

 156, which are of the usual form, the data presented give first place to 

 accurate work. Two values are entered for each subject: (1) the 

 number of columns of 10 digits correctly added during the 10-minute 

 interval, and (2) the percentage of the total number of added columns 

 whose sums were incorrect. For illustration, Bro of Squad A on Sep- 

 tember 29 added a total of 50 columns. Of these, 8 were incorrectly 

 added. He therefore has a score on that date, as shown in table 155, 

 of 42 columns correct and 16 per cent of errors. Can on the same 

 date added a total of 30 columns, of which 6 were in error. His score 

 is consequently 24 and 20 for correct columns and per cent error, 

 respectively. To convert the errors into per cent makes possible the 

 more direct comparison between subjects. The total number of 

 columns added, if desired, may be computed from the two values in 

 each of tables 155 and 156. For example, if the score for columns cor- 

 rect is 42 and the per cent of errors is 16, then 42 is 84 per cent of the 

 total columns. 



The individual variations among the members of Squad A are shown 

 in the low-diet averages in table 155. Fre, Tom, and Pea average 

 the largest number of correct columns in the time limit, with the values 

 of 76.0, 61.8, and 58.3. Subject Fre was a remarkably good adder, 

 but his case is of little interest to us, since he did not remain in the 

 squad and the data are very few. Of the other men, the two pre- 

 viously mentioned {Tom and Pea) were at the head of the group in 

 the normal experiment on September 29. In spiall percentage of 

 errors these men do not lead, however, in the average during the 

 low-diet period. Bro and Gar, with 4.3 and 8.0 per cent, have some- 

 what the advantage. Bro on October 13 and Pea on January 26 

 showed the only instances in which the subject's entire performance 

 was without error. While there is considerable fluctuation in an indi- 



