Cochran’s statistic *C*: |
where *s*_{max} is the largest standard deviation amongst the *s*_{i}. |

Mandel’s k-statistic |
Plot values for *k*_{ij} in the order of measurements made (by laboratory, e.g) and grouped by level. Draw in limits for 1% resp 5%. |

Range- (*R*-)diagram |
Plot values of the sample range, *R (= x*_{max}* – x*_{min}), against time. Action limits lie at *k*_{3}**s**_{r}. Warning limits lie at + *k*_{2}**s**_{r} |

F-test |
for the new (*n*) resp. old (*o*) measurements.Compare *F* with *F*_{max} for a certain number of number of degrees of freedom (= *j + k* – 2) and confidence level, which can be obtained from a table of overprocent points for the F-distribution (95%) resp. (99%). |

Process capability |
where *UTL* resp. *LTL* are the upper and lower tolerance limits, and *PS* is the process scatter, *s*_{p}. |

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