What is the mean of a set of measurements (xi) which have different
The more accurate values are more significant
than the less accurate ones. Accordingly we calculate a mean as
before but with each value weighted by the inverse of its variance: 1/(si)2.
in 10 values for xi and si
(hit Autofill, then Plot).
If the si
are consistent, we expect approx two thirds of the points to
lie within their si values of . Note,
if the si values are equal ( i.e. si =
s), the formula becomes as
for the sample mean.