Measurements, Biases and Uncertainties

A recent paper [1] in this journal, and later comments [2],[3] on that paper, indicate that there is a considerable amount of confusion in the area of measurements, biases, and uncertainties. It seems that most of this confusion results from the use of one term to identify two related but quite different quantities and then to attribute the characteristics of one of these quantities to the other. For example, the term "systematic error" is widely used to describe both a bias in a measurement and the uncertainty in that bias. Another example is when the same term is used for a measurement and the true value of the attribute being measured. The second of these has a definite constant, although unknown, value. The first will have a variance due to the randomness of the individual measurements.