PSY 201 1 Introduction to Statistics in Psychology PSY 201 Greg Francis PhD Department of Psychological Sciences Psychological Sciences Building Room 3174 765 494 6934 email gfrancis purdue edu http www1 psych purdue edu gfrancis Classes PSY201 Homework 12 Due 12 November 2009 Hand in your answers on a separate sheet of paper 1 A professor wants to investigate the relationship between test anxiety and test performance in intermediate statistics classes for older students and for younger students The professor believes that the relationship for the older students will be higher than for the younger students To test the belief the professor defines older as over 40 and younger as under 26 For random samples of 52 older students and 47 younger students the correlation between test anxiety and test performance are r1 0 48 and r2 0 22 respectively Test the null hypothesis H0 1 2 against Ha 1 2 with 0 05 2 A study is being conducted on the relationship between divergent thinking and science aptitude in boys and girls aged 12 to 14 years Random samples of size 120 each are selected from populations of boys and girls in this age range The sample members are administered a divergent thinking test and a science aptitutude test The correlation coefficients between the scores on these two tests are rG 0 69 for girls and rB 0 61 for boys Test the hypothesis H0 G B against Ha G 6 B Use 0 05 3 A researcher wants to test the hypothesis that the proportions of college men and women who smoke cigarettes are equal The researcher selects random samples of 10 of both males and females at a midwestern college and finds that 84 out of 210 males and 72 out of 240 females report that they smoke Test the null hypothesis P1 P2 against Ha P1 6 P2 with 0 05 4 A clinical psychologist in collaboration with a psychiatrist is interested in testing the anxietyreducing effects of two drugs X and Y In a random sample of 100 persons treated with drug X 75 report some relief of symptoms in a second random sample 105 of 160 persons treated with drug Y report some relief Is there evidence that the proportions of people reporting relief are different for users of the different drugs Test H0 P1 P2 against Ha P1 6 P2 with 0 05 5 A sociologist randomly selects 50 married couples in order to study the impact of parent effectiveness training PET on attitudes toward the use of behavior modification techniques Before and 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 Test H0 p 0 against Ha p 6 0 with 0 05 Before Yes No After No Yes 5 10 20 15 PSY 201 2 6 A psychology instructor is completing an item analysis of the final examination given to all freshmen psychology students The instructor is interested in whether the proportion of students who answer item 5 correctly differs from the proportion who answer item 7 correctly The data are in the table Test H0 p 0 against Ha p 6 0 with 0 05 Item 7 Incorrect Correct Item 5 Correct Incorrect 12 30 31 7
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