PSY 555 Homework 10

Chapter 5: #17,18,27,28

1. A researcher has 9 pictures he can use in his study. Pictures must be shown in pairs (and the order of the pairings doesn’t matter). His research assistant has lost 3 of the pictures. How many different pairings of pictures has the researcher lost by losing the three pictures?

2. Given that p=2/5, q=3/5, and N=230, what is the probability of getting a score of 110 or greater?

3. Describe the central limit theorem and discuss its importance.

4. Why are degrees of freedom used and why are the number of degrees of freedom dependent upon the type of test being performed?

5. Why does the t-distribution begin to approximate the z-distribution as N approaches infinity?