2. Error types

While the source tells us where error comes from, it doesn’t tell us how it behaves; the error type does. There are technically three error types. “Technically” since some people don’t consider mistakes a type of error, but we’ll include it as it does affect measurements if present.

We'll briefly introduce error types and their effect on accuracy and precision in this chapter. Following chapters address each error in more detail and how they can be compensated or analyzed.

a. Mistake

A mistake is usually the result of carelessness or misunderstanding. Mistakes are generally isolated and stick out in a measurement set. They are common for people learning to use equipment for the first time - something gets forgotten, a wrong button is pushed, digits are transposed, etc.

b. Systematic

A systematic error is one which conforms to some mathematical or physical principle. This allows a systematic error to be compensated, provided we have enough information or measurements are repeated in particular fashion. Depending on the character of the error, compensation could be computational, procedural, or mechanical.

c. Random

Random errors are those left when mistakes are eliminated and systematic errors are compensated. They are the only errors which prevent our knowing the true value of what we’re measuring. Random errors tend to be small and as likely to be positive as negative. Repeating measurements multiple times give random errors a change to cancel.