TY - JOUR AU - Landim, Tiago Ruckert AU - Jardim, Felipe Schoemer AU - Oprime, Pedro Carlos PY - 2021/04/23 Y2 - 2024/03/28 TI - Modified control chart for monitoring the variance JF - Brazilian Journal of Operations & Production Management JA - BJO&PM VL - 18 IS - 3 SE - Research paper DO - 10.14488/BJOPM.2021.015 UR - https://bjopm.org.br/bjopm/article/view/1129 SP - 1-10 AB - <p><strong>ABSTRACT.</strong></p><p><strong>Goal:</strong> The main objective of this research paper is to propose a chart, named &nbsp;Modified Control Chart, where the process variance () is allowed to be larger than the in-control variance value () until a maximum value (), as long as the process remains capable, in the sense that it produces a specified (tolerated) small fraction of non-conforming items.</p><p><strong>Design / Methodology / Approach: </strong>The research methodology was quantitative approach with statistical analysis of simulated data, to assess the practical impact of variance increase in process control in terms of quality requirements.</p><p><strong>Results: </strong>The analysis of the simulated data showed that by using the proposed &nbsp;Modified Control Chart the number of unnecessary interventions in the process could be decreased, contributing to improve its efficiency.</p><p><strong>Limitations of the investigation: </strong>The analysis assumed mean and variance known, which is unlikely to occur in real applications. Research considering unknown parameters is also in progress.</p><p><strong>Practical implications: </strong>The S<sup>2</sup> Modified Control Chart detects only genuinely increases in the process variance, which significantly increase the rate of non-conforming items being produced, preventing unnecessary process stop and assessment for assignable causes if only a small increase in the process variance occurs, contributing for higher process efficiency and reduce costs.</p><p><strong>Originality / Value: </strong>This paper introduces a new control chart to monitor the variance of quality characteristics being produced by capable processes, preventing process overcontrol.</p> ER -