Accuracy and Precision

Reblog from original site esfscience.

Physics and Chemistry for IG and A level

IB exam questions sometimes ask you to think about the difference between accuracy and precision of a set of measurements. Ideally a measurement device is both accurate and precise, with measurements all close to and tightly clustered around the known value. The accuracy and precision of a measurement process is usually established by repeatedly measuring some traceable reference standard. Such standards are defined in the SI system – the whole community knows and uses the same standard values for metres, seconds and so on.

The accuracy of a system of measurement is the degree of closeness of repeated measurements of a particular quantity to that quantity’s actual (true) value.

The precision of a measurement system, also called its repeatability is the degree to which repeated measurements under unchanged conditions show the same result.

We should also incorporate the idea of ‘trueness’. Trueness refers to the closeness of the mean of…

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