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CHAPTER 8: Complex Designs 277CHALLENGE QUESTIONS1 Consider an experiment in which two independentvariables have been manipulated. Variable A hasbeen manipulated at three levels, and Variable Bhas been manipulated at two levels.A Draw a graph showing a main effect ofVariable B, no main effect of Variable A, and nointeraction effect between the two variables.B Draw a graph showing no main effect ofVariable A, no main effect of Variable B, but aninteraction effect between the two variables.C Draw a graph showing a main effect of Variable A,a main effect of Variable B, and no interactioneffect between the A and B variables.2 A researcher has used a complex design to studythe effects of training (untrained and trained) andproblem difficulty (easy and hard) on participants’problem-solving ability. The researcher tested atotal of 80 participants, with 20 randomly assignedto each of the four groups resulting from thefactorial combination of the two independentvariables. The data presented below represent themean percentage of the problems that participantssolved in each of the four conditions.TrainingProblem Difficulty Untrained TrainedEasy 90 95Hard 30 60A Is there evidence of a possible interaction effectin this experiment?B What aspect of the results of this experimentwould lead you to be hesitant to interpret aninteraction effect if one were present in thisexperiment?C How could the researcher modify theexperiment so as to be able to interpret aninteraction effect if it should occur?3 A psychologist is interested in whether olderpeople suffer a deficit with respect to their reactiontime in processing complex visual patterns. Fifty65-year-old people and 50 college-age youngadults volunteer to participate in the experiment.The participants are tested using an embeddedfigures test. The psychologist presents a simplefigure to each participant followed immediately bya complex pattern that contains the simple figure.The participant must indicate as quickly as possiblethe location of the simple figure in the complexpattern. Participants are timed from the onset of thecomplex pattern until they locate the simple pattern.As the psychologist had expected, the meanreaction times for the older adults were markedlylonger than those for the young adults. By anystandard the results were statistically significant.A The psychologist claims based on theseresults that the differences in reaction timesin this experiment were caused by a deficit inthe older adults’ ability to process complexinformation. You recognize that a complexdesign experiment would need to be donebefore he could conclude that older adultssuffered a deficit in their processing of complexvisual patterns. What additional reaction-timetest could the psychologist give to both groupsin order to make his experiment into a complexdesign? Describe an outcome of the complexdesign experiment that would support the claimthat older adults suffer a deficit in processingcomplex information and another outcome thatwould lead you to question the claim.B Recognizing that his original study is flawed, thepsychologist tries to use post hoc (after the fact)matching to try to equate his two groups. Hedecides to match on general health (i.e., the betteryour general health, the faster your reaction time).Although he cannot get an exact matching acrossgroups, he does find that when he looks only atthe 15 healthiest older adults, their reaction timesare only slightly longer than the mean for theyoung adults. Explain how this outcome wouldchange the psychologist’s conclusion concerningthe effect of age on reaction time. Could thepsychologist reach the general conclusion thatolder adults do not suffer a deficit in reaction timein this task? Why or why not?Answer to Stretching Exercise I1 (a) Actual guilt: M 3.04, Actual innocence: M 3.18(b) The difference between the means for the suspect-status independent variable is 0.14,which is a very small difference compared to the mean difference observed for the statisticallysignificant effect of interrogator expectation on the number of presumptive questions(3.62 2.60 1.02).