The meaning of the uncertainty in physical measurements

Almost every time you make a measurement, the result will not be an exact number, but it will be a range of possible values. The range of values associated with a measurement is described by the uncertainty. The uncertainty is a number which follows the ± sign. For example, in the measurement (8 ± 2), 8 is the value, and 2 is the uncertainty. Since all of science depends on measurements, it is important to understand uncertainties and get used to using them. The uncertainty in a measurement is sometimes called the “error”. This is an outdated term, because the word “error” implies that some kind of a mistake has been made. On the contrary, uncertainty is a necessary part of any measurement, and it would be a mistake not to report it.

Calcul d'erreurs

Estimating the uncertainty of physical measurements

Two different measurement methods have to be distinguished, direct and indirect measurement

Definition

An error may be defined as the difference between the measured and actual values.

δ e = x r x m %delta _{e}= x_{r}- x_{m}

Where x_r is the real value (experimentally the average value), and x_m : is the real value measured.