Surely Variance is only useful in Manufacturing?

No. It is true that the principles of variance were first widely used in manufacturing in Japan. The Quality Control movement, led by Professor Deming, certainly gave Japan a massive competitive advantage for over thirty years. However, the same advantage can be gained by using variance and trends to control and improve any of the Critical Success Factors of any Service.

However, one fact that very few people realise is that using such techniques can also dramatically improve the motivation and skill levels of those involved.