Comparison of Individual and Moving Range Chart Combinations to Individual Charts in Terms of ARL after Designing for a Common â•œAll OKâ•š ARL
نویسندگان
چکیده
In some process monitoring situations, consecutive measurements are spaced widely apart in time, making monitoring process aim and spread difficult. This study uses three cases to compare the effectiveness of two such monitoring schemes, i.e., the X chart alone (X-only chart) and the Individuals and Moving Range Chart Combination (X/MR chars), in terms of Average Run Length (ARL) after designing for a common " all OK " (in-control) ARL. The study finds that X chart alone is sufficient (and hence, recommended) in detecting changes in all the 3 cases: changes in the process mean, changes in the process standard deviation, and changes in both process mean and standard deviation.
منابع مشابه
Individual and Moving Ratio Charts for Weibull Processes
This article proposes methods for monitoring Weibull processes when data collection is restricted to one observation per sampling period. Because the Weibull distribution is an asymmetric distribution, it is not appropriate to apply normal-based individuals-movingrange charts to Weibull data. A transformation of Weibull to approximate normality prior to applying normal-based methods has been su...
متن کاملMonitoring and Change Point Estimation of AR(1) Autocorrelated Polynomial Profiles
In this paper, a remedial measure is first proposed to eliminate the effect of autocorrelation in phase-ІІ monitoring of autocorrelated polynomial profiles, where there is a first order autoregressive (AR(1)) relation between the error terms in each profile. Then, a control chart based on the generalized linear test (GLT) is proposed to monitor the coefficients of polynomial profiles and an R-c...
متن کاملControl chart based on residues: Is a good methodology to detect outliers?
The purpose of this article is to evaluate the application of forecasting models along with the use of residual control charts to assess production processes whose samples have autocorrelation characteristics. The main objective is to determine the efficiency of control charts for individual observations (CCIO) and exponentially weighted moving average (EWMA) charts when they are applied to res...
متن کاملOn the Sample Size Problem for X and X Shewhart Control Charts for a Mean and Implications for Designing Q-charts
In this work we study the question of how much data is required in order for classical X and X charts with estimated control limits to perform essentially like charts with the true control limits. The results indicate that using estimated control limits results in charts on which the events that individual points exceed control limits are dependent events, and that one result of this dependence...
متن کاملA Self-starting Control Chart for Simultaneous Monitoring of Mean and Variance of Simple Linear Profiles
In many processes in real practice at the start-up stages the process parameters are not known a priori and there are no initial samples or data for executing Phase I monitoring and estimating the process parameters. In addition, the practitioners are interested in using one control chart instead of two or more for monitoring location and variability of processes. In this paper, we consider a s...
متن کامل