## Independent Samples

## Once you have determined that the values are independent, another factor must be determined:

## Question no.2:

Are the variances of both populations known?## Approximate with s if BOTH sample sizes

n_{1 },n_{2}happen to exceed 30.

## YES.

Because we know the population variance, or the sample size is greater than 30, we can conduct a test involving the standard normal distribution (the z-test). You can see the similarity between tests of the mean involving one variable and those involving two.

## NO.

If the sample size does not permit us to approximate the population variance, we must perform an F-test on the sample variances to determine how to proceed.

5:19