The standard deviation of each parameter should be calculated from at least 30 individual results, based on the same target for that parameter. Any change of target during the period when the data has been collected will lead to the standard deviation being skewed and the results will not be statistically representative. The samples themselves should be daily spot samples taken from the process.
Understanding your results
The result of the Variability Calculator for each material is a percentage score. A score of 100% would mean that the variability of all parameters is to the target levels expected by CPI to ensure optimum performance. A score of less than 100% indicates that there is a less than optimal variability in one or more of the parameters in the calculation. The score is calculated by comparing the target variability and then weighted dependent upon its overall impact on the process and product.
Results Colour Key
Your overall result/percentage, as well as each individual parameter is colour-coded based on the values you enter:
Green - your process is under control with respect to the CPI variability parameters
Orange - your process variability is average which may represent an opportunity for improvement
Red - your process variability is outside the targets set by CPI and improvement in this parameter will result in a productivity improvement
If you would like to talk to CPI about variability and process improvement services please Contact Us.