0.4 0.5 0.6 0.7 0.8 0.9 1.0 



Fig. 6 — Cumulative probability 



VALUE OF pn 



curves— Poisson exponential. For determining probability of occurrence of c or less defects in a sample of n pieces selected from an infinite 

 fication of chart given by Miss F. Thomdilie B. S. T. J., October 1926). 



in which the fraction defective is p {A modi- 



