Type A evaluation of uncertainty

A Type A evaluation of uncertainty obtains an uncertainty component through statistical analysis of observations. For independent repeated readings with sample standard deviation $s$, the estimated standard uncertainty of their mean is $s/\sqrt{n}$.

Independence and stability matter: serially correlated readings do not generally provide $n$ independent pieces of information. Type A and Type B evaluation of uncertainty classify how components are assessed, rather than separating random measurement errors from systematic error.^[ref]