What two assumptions must be met when you are using the z te

What two assumptions must be met when you are using the z test to test differences between two means?

Can the sample standard deviations s1 and s2 be used in place of the population standard deviations 1 and 2?

It only has to be 100 words.

Solution

Following are the assumptions:

1.

Both samples must be independent to each other. There should be no relationship between the observations in each sample.

2.

The populations under study (from which samples are drawn) must be normally distributed. And the population standard deviations of the variable must be known.

----------------

In case 1 and 2 are unknown, the sample standard deviations s1 and s2 can be used but in that case the sample sizes must be greater than or equal to 30.