PSY 555 Homework 7


Chapter 4: #3,4,5,7,9,13,14,15,17,20 (draw and shade the distribution when applicable and show all steps of the hypothesis test)


1.   If a researcher normally uses an alpha level of .01, but this time used an alpha level of

.05, what does this do to the amount of power?  How does this affect the risk of a Type I error?


2.   A researcher is trying to assess the effects of drug use on IQ.  For the population, the

average IQ is =100 and =15.  The following data consists of IQ scores for a sample of cocaine addicts:


85, 90, 99, 103, 100, 86, 97, 83, 101, 91, 87


Do the IQ scores of cocaine addicts significantly differ from those of the population?  Test at the .01 level of significance and show all four steps of the hypothesis test.


3.   A researcher at a drug company is testing the effectiveness of a new drug that slows down

the progression of AIDS.  Should the researcher examine his data using a .05 or .01 level of significance?  Justify your answer with regards to the risks of Type I and Type II errors.