x̅ and R chart
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In statistical process control (SPC), the and R chart is a type of scheme, popularly known as control chart, used to monitor the mean and range of a normally distributed variables simultaneously, when samples are collected at regular intervals from a business or industrial process.[1] It is often used to monitor the variables data but the performance of the and R chart may suffer when the normality assumption is not valid.
Quick Facts x ¯ {\displaystyle {\bar {x}}} and R chart, Originally proposed by ...
and R chart | |
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Originally proposed by | Walter A. Shewhart |
Process observations | |
Rational subgroup size | 1 < n ≤ 10 |
Measurement type | Average quality characteristic per unit |
Quality characteristic type | Variables data |
Underlying distribution | Normal distribution |
Performance | |
Size of shift to detect | ≥ 1.5σ |
Process variation chart | |
Center line | |
Upper control limit | |
Lower control limit | |
Plotted statistic | Ri = max(xj) - min(xj) |
Process mean chart | |
Center line | |
Control limits | |
Plotted statistic |
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