Question

for 2 independent samples..what is the rule for eyeballing the variance to choose either the pooled or unpooled method.

given a sample 1 variate equal 2699 and sample 2 variation of 3834. which variance method to use?

Answer 1

Comparing two proportions – For proportions there consideration to using "pooled" or "unpooled" is based on the hypothesis: if testing "no difference" between the two proportions then we will pool the variance, however, if testing for a specific difference (e.g. the difference between two proportions is 0.1, 0.02, etc --- i.e. the value in Ho is a number other than 0) then unpooled will be used."

Also for pooled variance to use equal population variance is assumed.

Here we have different variances 2699 and 3834 respectively.

Hence,pooled variance assumption is voilated and we would use unpooled Variance