Economic ordering quantity models for items with imperfect quality

In this paper, we first look at the issue of non-shortages in models with proportional imperfect quality, when the proportion of the imperfects is a random variable. More specifically we revisit the papers of Salameh and Jaber (Int. J. Prod. Econom. 64 (2000) 59) and Chan et al. (Prod. Plann. Control 14 (2003) 588) and we point out that the sufficient conditions given in these papers to ensure that shortages will not occur may not really prevent their occurrence. Next, considering the timing of withdrawing the imperfect quality items from stock, we clarify a point not clearly stated in Salameh and Jaber (Int. J. Prod. Econom. 64 (2000) 59) and we extented this model to the case in which withdrawing takes place at the end of the planning horizon. Finally, we establish that the objective of maximizing the mean average profit, which was set in Salameh and Jaber (Int. J. Prod. Econom. 64 (2000) 59), is superfluous and the results given there can be obtained by ignoring the revenue issues assumed in the model and minimizing directly the mean average cost.