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In statistical quality control, the individual/moving-range chart is a type of control chart used to monitor variables data from a business or industrial process for which it is impractical to use rational subgroups. [1] The chart is necessary in the following situations: [2]: 231
Control charts are graphical plots used in production control to determine whether quality and manufacturing processes are being controlled under stable conditions. (ISO 7870-1) [1] The hourly status is arranged on the graph, and the occurrence of abnormalities is judged based on the presence of data that differs from the conventional trend or deviates from the control limit line.
As with the ¯ and R and individuals control charts, the ¯ chart is only valid if the within-sample variability is constant. [5] Thus, the s chart is examined before the ¯ chart; if the s chart indicates the sample variability is in statistical control, then the ¯ chart is examined to determine if the sample mean is also in statistical control.
As with the ¯ and s and individuals control charts, the ¯ chart is only valid if the within-sample variability is constant. [4] Thus, the R chart is examined before the ¯ chart; if the R chart indicates the sample variability is in statistical control, then the ¯ chart is examined to determine if the sample mean is also in statistical control.
The EWMA chart is sensitive to small shifts in the process mean, but does not match the ability of Shewhart-style charts (namely the ¯ and R and ¯ and s charts) to detect larger shifts. [ 2 ] : 412 One author recommends superimposing the EWMA chart on top of a suitable Shewhart-style chart with widened control limits in order to detect both ...
In industrial statistics, the X-bar chart is a type of variable control chart [1] that is used to monitor the arithmetic means of successive samples of constant size, n. This type of control chart is used for characteristics that can be measured on a continuous scale, such as weight, temperature, thickness etc.
The probability of nonconformity at any location is small and constant The inspection procedure is same for each sample and is carried out consistently from sample to sample The control limits for this chart type are c ¯ ± 3 c ¯ {\displaystyle {\bar {c}}\pm 3{\sqrt {\bar {c}}}} where c ¯ {\displaystyle {\bar {c}}} is the estimate of the ...
Regression control chart differs from a traditional control chart in four main aspects: It is designed to control a varying (rather than a constant) average. The control limit lines are parallel to the regression line rather than the horizontal line. The computations here are much more complex. It is appropriate for use in more complex ...