Don’t Confuse Precision with Accuracy

I’ve just read a thread from @RonJeffries in which he talks, as eloquently as ever, about precision.

Pin the tail

It reminded me of a discussion I’ve had several times with various people over a long period of time – the difference between accuracy and precision.

More importantly, the dangers of confusing the two.

Us humans have a tendency to attribute accuracy to something that is stated with a high degree of precision.  Stating that a task is going to cost £153 is, somehow, more convincing than saying ‘around £200, maybe a little less’.

I’ve seen this played out most often in the traditional project planning  dance, where a quick effort estimate based on one-line requirements (and therefore liable to inaccuracy) is layered with precision around resource usage, dependency mapping, critical path analysis…  The resulting plan appears so precise that we forget the pedigree of its foundations – the original guess.

Agile and Lean provides many and varied mitigation strategies – but the first step is to notice it early enough to react.

The image shows some children playing ‘Pin the Tail on the Donkey’. A rather weird concept for a game, but seems strangely relevant somehow

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