ABSTILACTS OF TECHNICAL ARTICLES 685 



tion of candidates suitable for the fenestration operation for the restoration 

 of hearing in otosclerosis (immobilized stapes). The present paper is con- 

 cerned with an investigation of short time auditory fatigue as a method of 

 obtaining an impairment analysis. In this study, it was found that the 

 fatigue of the conductively deafened observer was similar to the normal 

 observer except the onset of fatigue was shifted by the amount of the thresh- 

 old loss. For the nerve deafened observer, on the other hand, the onset of 

 fatigue was found to occur at normal intensity levels. The occurrence of 

 excessive fatigue in one of the nerve type impairment cases investigated 

 appears to offer additional information on the nature of the lesion. 



A Sampling Procedure for Design Tests of Electron Tubes {Sponsored by 

 Joint Electron Tube Engineering Council)}^ S. W. HoRROCKS, P. M. 

 DiCKERSON, H. F. Dodge,* E. R. Ott, H. G. Romig,* W. B. Rupp, J. R. 

 Steen, R. E. Wareham, and A. K. Wright. The Committee on Sampling 

 Procedure was established on July 21, 1943 as part of the Electron Tube 

 Section of the Radio Manufacturers Association (RMA). The purpose of 

 the Committee is to develop sampling methods and to act in an advisory 

 capacity towards standardization of Sampling Procedures throughout the 

 Electron Tube industry. This Committee was later embodied as a main 

 Committee of the Joint Electron Tube Engineering Council of the RMA 

 and NEMA. This Council was established in 1945 to handle all engineering 

 matters for the Electron Tube industry for both trade associations. Radio 

 Manufacturers Association and National Electrical Manufacturers Asso- 

 ciation. 



One of the earliest projects handled by the Committee was the develop- 

 ment of a statistically sound sampling inspection procedure for so-called 

 "design tests" of electron tubes. In general, design tests relate to character- 

 istics that are normally quite stable and are relatively less important to the 

 consumer. The nature of these tests is such that only relatively small 

 samples are practicable. The Joint Army-Navy Specification JAN-IA 

 incorporated a sampling plan for design tests allowing (1) not more than 10% 

 of the sample tubes to contain design test defects of any one kind and (2) 

 not more than 20% of the sample tubes to contain design test defects of any 

 kind. Because of the extremely wide range in lot sizes for different classes 

 of electron tubes, such a simplified sampling plan was m effect too strict for 

 small lot sizes and too liberal for large lot sizes. Moreover, no distinction 

 was made in the relative seriousness of different kinds of design test defects. 

 The Committee accordingly set about to prepare a sampling inspection plan 

 that would be relatively free of these faults. The new procedure covers all 



'" Industrial Quality Control, November 1946. 

 * Of Bell Tel. Labs. 



