Accuracy and precision

This is an important distinction for scientists in all fields to understand. One of the first things I tell the undergraduate students, is to be precise in your experiments and accurate in your measurements. The definition of accuracy is 'the condition or quality of being true, correct, or exact;freedom from error or defect; precision or exactness;correctness.' Precision is 'characterised by or having a high degree of exactness.' (Collins English Dictionary – Complete and Unabridged © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003).

For example, if the experiment is to measure the number of times a subject will jump if tapped on the knee for one minute, the experiment should be described precisely so that anyone wishing to reproduce the findings will carry it out in exactly the same way. The measurements, that is, the count of the number of times the subject will jump, must be accurate. If the subject jumps eleven times but the scientist records it as approximately ten times, that is not accurate.

I have simplified the example here to demonstrate the principle, but it matters in real life too. When making jam or confectionary, you need an accurate thermometer. Raymond Blanc says you need to weigh your egg whites precisely, or the macaroons will be pah!

And in a court of law, the barrister will ask you to be precise about your eye witness account, so that the court will be able to make an accurate assessment of the case.

So you see, accuracy and precision is more than just a phrase used by the boys and girls in white coats. It underpins many aspects of our modern lives, try it for yourself.

Follow @Shackleford_LB