PSY 201 1Introduction to Statistics in Psychology: PSY 201Greg Francis, PhDDepartment of Psychological SciencesPsychological Sciences Building, Room 3174(765) 494-6934email: [email protected]://www1.psych.purdue.edu/∼gfrancis/Classes/PSY201/Homework 12Due: 12 November 2009Hand in your answers on a separate sheet of paper.(1) A professor wants to investigate the relationship between test anxiety and test performance inintermediate statistics classes for older students and for younger students. The professor believesthat the relationship for the older students will be higher than for the younger students. To test thebelief, the professor defines “older” as over 40 and “younger” as under 26. For random samples of 52older students and 47 younger students, the correlation between test anxiety and test performanceare r1= 0.48 and r2= 0.22, respectively. Test the null hypothesis H0: ρ1= ρ2against Ha: ρ1> ρ2with α = 0.05.(2) A study is being conducted on the relationship between divergent thinking and science aptitudein boys and girls aged 12 to 14 years. Random samples of size 120 each are selected from populationsof boys and girls in this age range. The sample members are administered a divergent-thinking testand a science-aptitutude test. The correlation coefficients between the scores on these two tests arerG= 0.69 for girls and rB= 0.61 for boys. Test the hypothesis H0: ρG= ρBagainst Ha: ρG6= ρB.Use α = 0.05.(3) A researcher wants to test the hypothesis that the proportions of college men and womenwho smoke cigarettes are equal. The researcher selects random samples of 10% of both males andfemales at a midwestern college and finds that 84 out of 210 males and 72 out of 240 females reportthat they smoke. Test the null hypothesis P1= P2against Ha: P16= P2with α = 0.05.(4) A clinical psychologist, in collaboration with a psychiatrist, is interested in testing the anxiety-reducing effects of two drugs, X and Y . In a random sample of 100 persons treated with drug X, 75report some relief of symptoms; in a second random sample, 105 of 160 persons treated with drugY report some relief. Is there evidence that the proportions of people reporting relief are differentfor users of the different drugs? Test H0: P1= P2against Ha: P16= P2with α = 0.05.(5) A sociologist randomly selects 50 married couples in order to study the impact of parent effec-tiveness training (PET) on attitudes toward the use of behavior-modification techniques. Beforeand after PET classes, couples are asked whether or not they favor the use of such techniques.The results are in the table. Test whether the the classes changed the parents’ attitudes. TestH0: δp= 0 against Ha: δp6= 0 with α = 0.05.AfterNo YesBefore Yes 5 10No 20 15PSY 201 2(6) A psychology instructor is completing an item analysis of the final examination given to allfreshmen psychology students. The instructor is interested in whether the proportion of studentswho answer item 5 correctly differs from the proportion who answer item 7 correctly. The data arein the table. Test H0: δp= 0 against Ha: δp6= 0 with α = 0.05.Item 5Correct IncorrectItem 7 Incorrect 12 30Correct 31
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