Bagan Kendali Variansi dengan Penambahan Variabel pada Nilai Ekspor dan Berat Ekspor

Abstract

To create products or services that meet certain quality standards, supervision and control need to be carried out. Quality control monitors changes in the level of variability, or the level of average, or both to observe changes that occur during the production process. The monitoring stage begins with controlling variability, followed by controlling the average level. Walter A. Shewhart (1920) introduced several variability control charts, including the S² variance control chart, which involves one quality characteristic, Y. Riaz (2008) introduced a regression-type estimator of the variance of Y using additional correlated information X. This control chart is known as the V_r control chart and shows better results than the S² control chart. Furthermore, Riaz (2009) introduced a V_t control chart, created based on a ratio-type estimator of the variance of Y. The accuracy of the V_t control chart increases as the value increases. The S², V_r, V_t control chart is used to monitor the variability of export value (Y) using additional information on export weight (X). All three charts indicate that the variability in export values is out of control. Comparison of the results obtained from the V_t, V_r, and S² control charts is made by examining the power curve of each chart. Specifically, it was observed that the V_t control chart produces more consistent and accurate conclusions.