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 This is an outdated term, because the word “error” implies that some kind of a mistake has been made.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.
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.
Where x_r is the real value (experimentally the average value), and x_m : is the real value measured.