Z-MR Chart -
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Z-MR Chart -
Options Stat > Control Charts > Variables Charts for Individuals > Z-MR > Z-MR Options > Estimate
Use to enter historical data for standardizing the data.
Method for estimating the standard deviation
How to define groups of observations
By runs: Choose to estimate s for each run independently. See Methods and formulas for information on choosing an estimation method.
By parts (combine all observations for same part): Choose to combine the data from runs of the same part, then estimate s for that part. This is repeated to estimate s for all parts.
Constant (combine all observations): Choose to pool all the data - across runs and parts - to obtain a common estimate of s.
Relative to size (combine all observations, use ln): Choose to take the natural log of the data, then pool the transformed data - across all runs and parts - to obtain a common estimate of s for the transformed data. The natural log transformation stabilizes the variation in cases where variation increases as the size of the measurement increases.
For each group, calculate
Average Moving Range: Choose to estimate s using the average of the moving range.
Median Moving Range: Choose to estimate s using the median of the moving range.
Length of moving range: Enter the length of the moving range. By default, Minitab uses a span of two because consecutive values have the greatest chance of being alike. The span must be < 100.