An Adjusted Economic Cost Model for Sampling Inspection Plans

Acceptance sampling inspection performed during inspection of incoming lot of raw materials or finished products where decision is taken either to accept or reject the inspected lot. Defective units of the products detected at the manufacturers’ site are either reworked or treated as scrap resulting in Internal failure cost while defective units of the product detected by the consumer after shipment are either returned to the producer or manufacturer or replaced resulting to external failure cost. This study therefore proposed an adjusted economic cost model with inspection error to achieve optimal sampling plan with minimized total cost. The model is tested on Rectifying Sigle sampling (RSS) and Rectifying Double Sampling (RDS) plans and comparison was made with the existing model. Findings from the study revealed that optimal sampling plan for RSS and RDS with minimal total cost was observed when the adjusted model with inspection error was used than in the existing model. It was also found that thetotal costs (TC) in RSS and RDS using the adjusted model were relatively smaller than in the existing model when the effect of changes in the values of Inspection cost Ci , Internal failure cost Cf and External failure cost Co on the optimal total cost were investigated. However, the total cost for RSS and RDS were found to be higher in the adjusted model when External failure cost Co ≥ 40than in the existing model. This adjusted model therefore performed better and is recommended to be used by all stakeholder in a supply chain