# Accuracy and Precision

Today I got asked what I thought was the difference between accuracy and precision as it pertains to relative estimation, I wasn’t ready for the question though and it’s been sitting on my mind bugging me so here are my thoughts:

I would think accuracy would be how close the estimation was to the truth and precision is how often you predict the same estimation given the same or similar complexity, in other words how repeatable you are. Accuracy is how right or wrong you are and precision is about how consistent you are (irrespective of right or wrong).

So, if you correctly estimate over and over, you’d be accurate and precise but if you estimate incorrectly, but are consistent about the “incorrectness” then you would be precise but not accurate. If you estimate correctly only every now and then for the same given complexity then you would be accurate but lack precision.

Interesting to hear what others think (like if I’ve lost my mind completely 🙂 )…

When reading the title I was “Ha! They are the same things!”. Well it seems I got it wrong. I found a pretty good definition over here http://en.wikipedia.org/wiki/Accuracy_and_precision. Since our field is one of computer “science” the definition might be quiet relative.

Keep at it Rick!

One more pretty fun illustration http://www.mathsisfun.com/accuracy-precision.html

Accuracy for me is about hitting the target, irrespective if you you get there whereas precision is all about the execution thereof. The execution was precise and the result accurate. My 1.5 cents 😉