The analysis produces the Analysis Of Mean Standard Deviations (ANOMS) chart when operators measure each part 9 or more times. The chart has a reference line at the average standard deviation across all parts measured by each operator. The chart includes decision limits that test for differences in test-retest error among operators.
Plotted points
The point for each operator is the weighted average standard deviation across all parts that each operator measures.
where
Centerline
For balanced data, the centerline is at the average of 
for the j operators. The following formula expresses this
average for balanced or unbalanced data.
where
Decision limits
- Upper Decision Limit (UDL)
- Lower Decision Limit (LDL)
where 
is the value of the centerline on the chart.
Notation
| Term | Description |
|---|---|
| nij | the number of measurements on part i by operator j |
| yijk | the kth measurement on part i by operator j |
 | the average of the measurements on part i by operator j |
 | The  critical value from the chi-square distribution with
vj degrees of freedom |
