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Practical sheet | REF: FIC1483 V1

Statistical monitoring of a batch of measuring instruments: inter-instrument comparison

Author: Pascal COQUET

Publication date: March 10, 2015 | Lire en français

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    3. Compare the equality of variances

    Several tests exist for comparing variances. For the purposes of this example, we have chosen the Cochran test because it deals with the highest variance. Indeed, it would be unfair to discard an instrument on the grounds of "too good a repeatability". We will therefore test the highest variance against all the others:

    C=SMax2∑i=1Nsi2

    If the C ratio is less than the Cochran critical value at 5% C CRIT...

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