2. Measurement Process Characterization
2.4. Gauge R & R studies
2.4.4. Analysis of variability

## Example of calculations

Example of repeatability calculations Short-term standard deviations based on
• J = 6 repetitions with 5 degrees of freedom
• K = 6 days
• L = 2 runs
were recorded with a probing instrument on Q = 5 wafers. The standard deviations were pooled over K = 6 days and L = 2 runs to give 60 degrees of freedom for each wafer. The pooling of repeatability standard deviations over the 5 wafers is demonstrated in the table below.
 Source of variability Sum of Squares (SS) Degrees of freedom (DF) Std Devs Repeatability $$SS_i = \nu_i \cdot {\large s}_{1i}^2$$ $$\nu_i$$ $${\large s}_1 = \sqrt{SS/\nu} \,\, \longrightarrow$$ Wafer #138 Wafer #139 Wafer #140 Wafer #141 Wafer #142 SUM 0.48115 0.69209 0.48483 1.21752 0.30076 3.17635 60 60 60 60 60 300 0.10290