Citation

Cho D, Najafi FT, Kopac PA. Transp. Res. Rec. 2011; 2228: 61-69.

Copyright

(Copyright © 2011, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.3141/2228-08

PMID

unavailable

Abstract

What is the optimum acceptance sample size (n)? Recent research by Gharaibeh and colleagues found that when incoming lots are anticipated to be high quality, the optimum n is relatively small (n = 3 for many acceptance quality characteristics). The finding was received with some skepticism, and many questions were raised about the optimization model and underlying assumptions. This paper summarizes follow-up research that more closely examined the optimization model elements and assumptions in an attempt to confirm or refute the finding by Gharaibeh and colleagues. By using a somewhat modified model and assumptions based where possible on actual data, the conclusions reached by Gharaibeh and colleagues stayed basically the same and several new conclusions were drawn. Some cautions are presented concerning the state highway agency use of small sample sizes. Agencies are encouraged to perform their own optimization calculations. By doing so, agencies will gain a better understanding of their acceptance plan systems and associated costs and will have greater confidence in applying economic decision analysis principles to minimize expected costs and optimize statistical acceptance risks.