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In the empirical sciences, the so-called three-sigma rule of thumb (or 3 σ rule) expresses a conventional heuristic that nearly all values are taken to lie within three standard deviations of the mean, and thus it is empirically useful to treat 99.7% probability as near certainty.
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.
The above eight rules apply to a chart of a variable value. A second chart, the moving range chart, can also be used but only with rules 1, 2, 3 and 4. Such a chart plots a graph of the maximum value - minimum value of N adjacent points against the time sample of the range.
The Western Electric rules are decision rules in statistical process control for detecting out-of-control or non-random conditions on control charts. [1] Locations of the observations relative to the control chart control limits (typically at ±3 standard deviations) and centerline indicate whether the process in question should be investigated for assignable causes.
The following example shows 20 observations of a process with a mean of 0 and a standard deviation of 0.5. From the Z {\displaystyle Z} column, it can be seen that X {\displaystyle X} never deviates by 3 standard deviations ( 3 σ {\displaystyle 3\sigma } ), so simply alerting on a high deviation will not detect a failure, whereas CUSUM shows ...
The fifth of six College Football Playoff top 25 rankings will be released on Tuesday, Dec. 3, after Week 14 games. What time is the next CFP rankings show? The College Football Playoff rankings ...
To help determine the capability of a process, statistically determined upper and lower limits are drawn on either side of a process mean on the control chart. [2] The control limits are set at three standard deviations on either side of the process mean, and are known as the upper control limit (UCL) and lower control limit (LCL) respectively ...