If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

Main content

Mean and standard deviation of difference of sample proportions


An educational researcher is studying two similar high schools in different states. Suppose that 50% of all 425 students at high school A have taken a college-level course, while 40% of all 525 students from high school B have taken such a course. The researcher plans on taking separate random samples of 50 students from each high school to look at the difference (AB) between the proportions of students who have taken a college-level course in each sample.
Consider the formula:
Why is it not appropriate for the researcher to use this formula for the standard deviation of p^Ap^B?
Choose 1 answer: