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BELL SYSTEM TECHNICAL JOURNAL 



suppose the possible number of occurrences n to be at least thirty 

 times the average a and at least 25, and that N, the number of samples 

 in the series, must be at least 50. This last requirement excludes 

 from our list a number of series which have pre\'iously been presented 



6 7 

 Values of a 



Fig. 6 — Typical finite binomial distributions for the probability that an event occur at 

 least c times in a group of n trials for which the average number of occurrences is a = np 



(a) a= 5, n= 10 



(b) a= 5, w = 100 



(c) a = 10, n= 20 



(d) a = 10, M = 100 



