Discover Deming, the theory of variations

Your job involves interpreting measurements or indicators, and making decisions based on these figures.

When an indicator deteriorates, you look for an explanation or a cause for this deterioration, either for yourself or because you've been asked, and you put in place action plans for improvement. When an indicator improves, on the other hand, you tend to consider that the actions implemented previously are bearing fruit, and should be maintained.

Changes in indicators or measurements are generally made by comparing the period under observation (e.g. the past week or month) with the previous period (the previous week or month) or with the same period in the previous year.

But are the usual methods of monitoring indicators or measurements always relevant? Does an apparent deterioration always call into question previous decisions? Should new actions be taken? Should we look for someone to blame, or ask everyone involved to "make an effort"?

This sheet deals with an essential aspect of Deming's philosophy: the theory of variation.