Assessing process accuracy - an inferential method about the process accuracy index

Process accuracy index C-a has been developed in the manufacturing industry to provide numerical measures on evaluating process centering. Distributional and inferential properties of the estimated accuracy index were investigated in the previous work. In this paper, a reliable hypotheses testing procedure on process centering for in-plant applications is constructed. Useful critical values to ensure the process reaching a certain desirable level of the time are tabulated. A practical example is also presented to illustrate how the proposed reliable procedure may be applied.