5/21/2023 0 Comments Xbar s chartIn the past, there has been reluctance to use the X-s chart in place of the X-R chart. The other chart is for the subgroup standard deviations (s). One chart is for the subgroup averages ( X). Like most other variables control charts, it is actually two charts. ![]() Time, density, weight, and length are examples of variables data. This type of control chart is used with variables data - data that is taken along a continuum. This month's newsletter introduces the X-s chart. This is where the X-s chart provides the solution. A different method is needed for the larger subgroup sizes. One problem with the X-R chart is that the range becomes a poorer and poorer measure of within-subgroup variation as the subgroup size increases. But with computer software, this is no longer an issue. This was important when the control chart calculations had to be done by hand or with a calculator. The range is an easy concept to understand - and to calculate. For the measurements within a subgroup, the range is the maximum - minimum value. This control chart uses the range to measure the variation within a subgroup. The most common control chart for years has been the X-R chart. Next month we will look at a detailed example of an X-s chart. This month we will introduce X-s charts and describe how they are constructed. But, the X-s chart might actually be the better chart to use. The X-s chart is often overlooked in favor of the X-R chart. ![]() This month's publication is the first part of a two part series on X-s charts.
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