Investigating the effect of measurement error on the performance of the signal control chart
Volume 4, Issue 1, Summer 2014, Pages 23-32
Majid Nojavan, Masoud Alishahi
Abstract The sign chart is one of the most common nonparametric charts used to control the centrality of processes with unknown or non-normal distributions. Considering the effect of measurement error on the performance of control charts, this paper examines the effect of measurement error on the performance of the sign chart using an additive model. For this purpose, a simulation program has been developed that calculates the average length of the sign chart sequence for three different distributions and in two states of awareness or ignorance of the existence of measurement error. The simulation results show that the performance of the sign chart for all three distributions and in both states is weakened by the effect of measurement error, and with an increase in the variance of the measurement error, the effect of the error on the performance of the chart increases. Also, the effect of increasing the number of measurements on reducing the effect of measurement error in the sign chart has been investigated. The results show that although using this method when aware of the existence of measurement error has a positive effect on the performance of the chart, if unaware of the existence of the error, this method weakens the performance of the sign chart.