THE ACQUISITION OF SKILL IN ARCHERY. 



121 



any of the other groups, with a somewhat greater amount of improvement. 

 The improvement shown by the 12-shot group is in part spurious, owing to 

 the method of recording the shots in this group. At the beginning of practice 

 many arrows fell short. These were recorded as failures. In computing the 

 averages these failures are counted all as 84 inches from the bulls-eye, which 

 was, probably, an overestimate, and added something near 6 or 8 inches to 

 the average records of the first 60 shots. 



The amount of improvement in the 5 groups has been expressed in three 

 ways: by the difference in average between the first and last 5 shots fired; 

 between the first and last 40 shots; and by the differences in the averages of 

 the first and last half of practice. These results are given in table 40. 



70 



60 



50 



40 



30 



10 



W 100 200 300 400 



FIG. 19. Learning curves for improvement in archery for 5 groups shooting 5, 12, 20, 

 40, and 60 shots daily. Arranged as in figure 13. 



The absolute improvement, measured by any of these methods, is greatest 

 in the 12- and 5-shot groups. The 60-shot group comes next with considerably 

 less improvement, and the 20- and 40-shot groups are about equal. It appears 

 from this that the rate of improvement per unit of practice is somewhat greater 

 when the practice is distributed over many days than when it is concentrated 

 into a few days. Whether there is a closer correspondence between the 

 distribution of practice and the amount of improvement is not brought out 

 by this method of treating the results, but an analysis of the data in a some- 



