Sample Size Determination for the Audit and Validation of an Industrial Process Control Outcome

This study is aimed at determining sample sizes at subgroup level and number of groups utilized in monitoring, evaluating and validating the reliability of an industrial process control output using a set of simulated data underlying the variable and attribute charts scenarios. The methodology adopts sample size estimation procedure using X̅ for the case of a variable control charts and P, NP,& C charts for the case of attribute control charts based on available information provided for the validation of reported quality control results. Findings shows that the possibility of process validation using of diverse provided specific information. A sample subgroup sample size of 3 and sample group number of 20 were estimated provided UCL of 17.5 corresponding to total mean of 227.2 and grand total of 681.6 for an x̅ control chart. Considering the attribute control chart for the proportion defective, a UCL of 0.801 yields an estimated subgroup sample size of 202 attributed to 0.773 overall proportion of defectives. A UCL of 11.08 resulted to an estimated sample size of 7 given a reported overall proportion of defective with attention drawn towards number of defectives all complemented by an estimation plot. However, the result above proves the estimation procedure as best suited in the validation of the reliability industrial process or reports to ascertain inclusively the effectiveness and accuracy of the internal or assigned inspection team.