Tests of Differences between Means, Independent Groups, Standard Deviation Estimated (3 of 8)
The estimated standard error,
, is computed assuming that the
variances in the two populations are
equal. If the two sample sizes are equal (n1 =
n2) then the population variance σ² (it is
the same in both populations) is estimated by using the following
formula:
where MSE (which stands for mean square error) is an estimate of σ². Once MSE is calculated,
can be computed as follows:
where n = n1 = n2. This formula is derived from the formula for the standard error of the difference between means when the variance is known.