## Criterion / Action

### Grubb’s G and Cochran’s C statistics

If G (Grubb) and C (Cochran) are:

• Less than or equal to their 5% critical value – accept
• Exceeding their 5% critical value but smaller than their 1% critical value – straggler (*)
• Exceeding their 1% critical value – “outlier” (**)

### Mandel h-statistics

If a measured datum has an h-statistic:

• Has a different character from all other data
• Is very distinct in value from the other data
• Depends systematically on the level

then the measurements made by that laboratory should be examined in, in particular.

### Mandel k-statistics

If a datum has a k-statistic which is:

• larger – this indicates that the lab has a worse repeatability
• smaller, indicating that the lab may have rounded their values too much, e.g.

then the measurements made by that laboratory should be examined in, in particular.

### Chart

Action must be taken if two consecutive results on a x-chart lie outside the warning limit.

### Range (R-) Chart

Action must be taken if two consecutive results on a R-chart lie outside the warning limit.

### T-test

If t <tmax of the Student t-test, the new measurements, combined older, where the new “pooled” average is calculated as:
where k, j are the number of measurements: new (n) resp. old (o).

### F-test

If F <Fmax of the F-test, the new measurements can be combined with the older, where the new “pooled” standard deviation is calculated as:

### Process capability (mean) (standdev)

When making a process capability test based on the mean:

If M <± 15%:                    Process is accepted

When making a process capability test based on the standard deviation:

If Cpk <1.0:                       Process must be improved immediately

If Cpk is  1.0 – 1.3:            Process (just) meets specification.

If Cpk> 1.0:                       Process is accepted

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