Now check out this link Confidence Interval
SAMPLE 1 SAMPLE 2
Sample size 56 Sample size 55
mean 3.2 mean 2.8
s. deviation 1.8 s deviation 1.5
How do i find the Estimated Standard Error of the difference between the 2 sample mean numbers.
i know that ESE is S / Square root of N
But dont know how to progress
The st. error is the estimate of the st. deviation.
NOW there are two cases here.
If you assume that the population variances are equal, you pool the sample variances.
The st. deviation of is the square root of the variance .
Since we usually do not know or we use the sample variances
and that's what we call the st. error, .
BUT in may cases we assume that and in that case we pool the two estimators,
here the st. error is which is the same as .