SKEDSOFT

Repeatability and Reproducibility:

Reproducibility is also known as the inherent precision of the measurement equipment.  Consider the probability density functions shown in Figure below .The density functions were constructed from measurements of the thickness of a piece of metal with Gage A and Gage B.  The density functions demonstrate that Gage B is more repeatable than Gage A.

Range & average method:

a)      The Range & Average Method computes the total measurement system variability, and allows the total measurement system variability to be separated into repeatability, reproducibility, and part variation.

b)      The ANOVA method, discussed in the next section, is preferred to the average range method.  The ANOVA method quantifies the interaction between repeatability and reproducibility, and is considered to be more accurate than the average and range Method.

c)       To quantify repeatability and reproducibility using average and range method, multiple parts, appraisers, and trials are required. 

d)      The recommended method is to use 10parts, 3 appraisers and 2 trials, for a total of 60 measurements.  The measurement system repeatability.