In a sigma chart, what is the precise reason for calculating Sigma separately for each subgroup rather than calculating grand average for sigma?
OPTIONS
- Sub group statistics are important to be represented
- Sub group sigma is generally more accurate
- Sub group sigma doesn’t introduce unnecessary special cause
- Range is considered better than Sigma
ANSWER
Sub group sigma doesn’t introduce unnecessary special cause
EXPLANATION
Sub group sigma doesn’t introduce unnecessary special cause – It is this reason why Sigma is calculated for each subgroup rather than calculating the grand sigma.