Any report that makes year-on-year comparisons is likely to mislead.

Here is a report from sales:

monthly sales

Clearly it shows a good start to the year but things went wrong in September and now we’re in trouble.

Are we? The same data in a capability chart shows an entirely different picture.


Tabular data do not predict what will happen, you can’t make decisions with them, they will not tell you when real changes have occurred, why do we use tabular data?

How much time do we waste justifying / explaining / defending differences which are merely caused by natural variation?