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CHAPTER 11: Data Analysis and Interpretation: Part I. Describing Data, Confidence Intervals, Correlation 3812 A developmental psychologist investigates the effectof mothers’ carrying behavior on infant sleep patterns.Specifically, the investigator solicits help from40 mothers of newborns. The psychologist trains20 mothers in a carrying method that presses thenewborn’s head against the mother’s breast; theother 20 mothers are not instructed in a particularcarrying method. All mothers are trained to recordthe number of hours their newborn sleeps each24-hour period. Records are kept for 3 monthsin both groups. The mean 24-hour sleep periodfor infants in the instructed group was 12.6 (SD 5.1);in the unin structed group the mean was 10.1(SD 6.3).A Calculate the 95% confidence interval for thedifference between the two means.B What may be said about the effect of trainingbased on an examination of the confidenceinterval for this experiment?C What is the effect size for this experiment?Interpret the effect size measure based onCohen’s guide lines for small, medium, andlarge effects.3 A researcher asks college students to play a demandingvideo game while listening to classicalmusic and while listening to hard rock. All of the10 students in the experiment play the video gamefor 15 minutes under each of the music conditions.Half of the students play while listening first toclassical music and then to hard rock music;the other half perform with the types of music inthe reverse order (see Chapter 7 for information oncounterbalancing in a repeated measures design).The dependent variable is the number of correct“hits” in the game over the 15-minute period. Thescores for the 10 students areStudent Classical Hard rock1 46 762 67 693 55 514 63 785 49 666 76 677 58 638 75 759 69 7810 77 85A Calculate the means for each condition.What trend do you see in the comparison ofmeans?B Calculate the estimated standard error of thedifference scores.C Find the 95% confidence interval for the differencebetween the two means in this repeatedmeasures design.D State a conclusion regarding the effect of typeof music on performance given the analysis ofthese results.4 A social psychologist seeks to determine therelation ship between a paper-and-pencil measureof preju dice and people’s attitudes toward racialprofiling as a crime deterrent. At the beginningof the semester, students in a general psychologyclass are asked to complete six differentquestionnaires. Among the questionnaires isa measure of prejudice. Later in the semester,students are invited to take part in an exper imentexamining attitudes about criminal behavior andlaw enforcement tactics. As part of the experi ment,students complete a questionnaire asking aboutattitudes toward racial profiling as a crime deterrent.The researcher wishes to find out if scores on theprejudice measure obtained earlier will predictpeo ple’s attitudes about racial profiling. Higherscores on the prejudice measure indicate greaterprejudice, and higher scores on the profiling scaleindicate greater support for racial profiling. Scoreson both measures are obtained for 22 students asfollows:Student 1 2 3 4 5 6 7 8 9 10 11Prejudice 19 15 22 12 9 19 16 21 24 13 10Profiling 7 6 9 6 4 7 8 9 5 5 7Student 12 13 14 15 16 17 18 19 20 21 22Prejudice 12 17 23 19 23 18 11 10 19 24 22Profiling 4 8 9 10 10 5 6 4 8 8 7A Draw a scatterplot showing the relationshipbetween these two measures.B Inspect the scatterplot and comment on thepres ence or absence of a linear trend in thedata.C Calculate a correlation coefficient for these dataand comment on the direction and strength ofthe relationship.D On the basis of the correlational analysis, theresearcher concludes that prejudicial thinkingcauses people to support racial profiling bylaw enforcement agencies. Comment on thisconclusion based on what you know aboutthe nature of correlational evidence.