Set up a test assuming that the null (H
) is true and see whether the
facts of our sample contradict that assumption.
Key question: How likely is it that we would observe a sample
difference (14.5-12.5 = 2 hrs) if the null (H
) were true?
If very unlikely, we will reject H
and support H
If not very unlikely, we will fail to
Two-sample hypothesis test
We want to know if UW students differ from WSU students in terms of average study
We draw a random sample of 100 UW students and find an average study time of
14.5 hours per week with a standard deviation of 8.25.
In contrast, our sample of 81
WSU students has an average study time of 12.5 hours per week with a standard
deviation of 7.0.
Use a .05 alpha level to test the statistical significance of the observed
difference between means.
Plan: State the HYPOTHESES