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THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1957 



in the alternative specification. We shall be interested in comparing the 

 alternative specification (P*, p*] , p*]) "with the original specification 

 with the same P* and with d* set equal to p*] — pf2] • It is clear that 

 the value of n required for the original specification will always be 

 larger. 



The original specification is simpler and is preferable to the alternative 

 specification when little or nothing is known about the processes on test, 

 but the price that has to be paid for ignorance is an increase in the 



0.05 0.10 0.15 0.20 0.26 0.30 0.35 0.40 0.45 Q50 



d 



Fig. 19 — Probability of a correct selection as a function of the true difference 

 ^ — Pdl ~" P(2i under the least favorable configuration for ^• = 3 and selected 

 values of n. 



