262 



BIOLOGICAL PROBLEMS 



of 72 to 82 occurred in 21 per cent of the cases, and 

 the best output of all, one of 82 to 92, in 3 per cent of 

 the cases. That is to say, the best workers in their 

 best weeks were able to achieve an hourly output just 

 about double that of the worst workers in their worst 

 weeks. I have found that a similar range of variation 

 occurs in many other munition operations, such as 



40 



20 



10 



o 



Tinte. Wbrkgrs 



Ptice-Wbrkgrs 



12 



22 ")2 42 5 2 62 T 2 

 Relative. Hourly Oiitiwt 



ig. 3. Variation in Output of Women sorting Cartridge Cases 



82 92 



turning fuse bodies, boring 3-inch shells, and in most 

 cartridge-case operations. I have found, moreover, 

 that the frequency of occurrence of the various output 

 values follows the same lines as are roughly indicated 

 in the curve shown on the right of fig. 3. The fre- 

 quency varies according to the laws of probability, or 

 the normal law of frequency of error. We find, for 

 instance, that if we sort out a large group of indivi- 

 duals according to their stature, a small proportion 



