The sample variance is the mean of the square of the deviations
of each measurement from the mean (called mean square deviation).
values: (hit Autofill and Plot) to see the sample
variance s2 and sample standard deviation s.
sum of deviations å(xi
- )= 0 is expected, since
it follows that
åxi = N,
is the definition of .
points (approx 2/3) lie within ± s of the mean .
must be at least 2, since we cannot estimate a spread in values from
a single measurement.
s is an
estimate of s, the standard deviation of a single measurement. It is not
an estimate of s(),
deviation of the mean ... next.