Statististical control tests based on Mean Values

v baserade på Medelvärden
Grubbs statistic Gpj:

One deviating result

Grubbwhere sj is the standard deviation of the mean
Two deviating results See ISO 5725-2:1994 §7.3.4.2
Mandel’s h-statistic Mandel_hPlot values for hij in the order of measurements made (by laboratory, e.g) and grouped by level.

Draw in limits for 1% resp 5%.

xbardiagram Plot values of the sample mean,xbar , against time.

Action limits lie at ± 3sr (UCL resp. LCL).

Warning limits lie at± 2sr

T-test tstatwhere k, j are the number of measurements: new (n) resp. old (o). Compare value of t with tmax, for a certain number of degrees of freedom (= j + k – 2) and confidence level, which can be obtained from a table of Student’s t critical values.
Process capability mcwhere M is the target value and TV is the tolerance width (i.e. half the tolerance interval).
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