Wednesday, September 20, 2006

Accuracy and Precision

This rattles around the back of my head on a regular basis, so I thought I'd cause it to be shaped by a stream of electrons travelling through a magnetic field and impacting a sheet of glass coated in Phosphorus compounds. Or something. It's based on a figure in a textbook I cannot otherwise remember, but it illustrates the distinction between accuracy (the extent to which a given measurement agrees with the standard value for that measurement) and precision (the extent to which a given set of measurements of the same sample agree with their mean). In other words, high precision means the shots hit the same spot, high accuracy means each shot hits where it's aimed.

Definitions from (specific definitions for Chemistry and Phsyics).

Edit: I release copyright on this image to the public domain. It took me less than 5 minutes to pull this together in PowerPoint and Photoshop, so I hold no great attachment for it. Take it, modify it, use it for whatever, I don't mind.


Carlo said...

I actually gave a presentation on accuracy and precision as they applied to science (and medicine) in the last class I TAed at SFU.

People throw those terms around like discarded cigarette butts, but they have very specific meanings (especially if your doing biochemical assays).

You can't teach anyone anything if they won't read about it themselves...

TheBrummell said...

Sometimes, learning by osmosis can be accomplished, without someone reading something by themselves.

The trick is that osmosis relies on solubility, so lots of water is needed. Also, the skull is a semipermeable membrane, so high pressures are involved.

I've found success with repeated beatings underwater.