Chapter 10 1 On the rst midterm exam in an introductory psychology class the grades are lower than Professor Mutola expected She suspects that multitasking is to blame She bans computers and cellphones from her class between the rst midterm and the second midterm When she compares the scores on the two exams for the people who had been using computers and cellphones she nds a signi cant improvement on the second exam When Professor Mutola rechecks her data she nds that the ve multitasking students with the lowest scores on the rst exam have dropped the class What threat to internal validity is this Attrition The rise in scores on the second test may be due to the loss of these extreme scores which is attrition 2 A city in California has asked Professor Rodriguez to conduct an experiment on earthquake preparedness Professor Rodriguez will assess the preparedness of a random sample of residents in the city and the city will mail out their annual brochure on earthquake safety Then two weeks later he will again assess the preparedness of those residents Right after the brochures are mailed a large earthquake is reported in Japan What threat to internal validity does this pose History The earthquake is an external or historical event that occurs to everyone in the study therefore the effect of the brochure cannot be assessed 3 The Ranschburg effect in short term memory involves repeated items if they are close together in a list recall is facilitated if they are far apart recall is impaired Francis designs an experiment on this effect using three conditions for a 12 animal names list no repetition repetition of the third animal as the fth item and repetition of the second animal as the tenth item Each item is viewed for one second then participants recall them in order Ten participants are tested in each condition The study showed null effects and large variability within the groups What is a likely solution Individual Differences Adding more participants to a study reduces the impact of individual differences within groups and will increase the chance of nding differences between groups 4 Lucia is interested in studying discrimination in hiring She designs an experiment in which the participant takes the role of an employer looking at job candidates for a speci c position The participant is given a resume and rates the suitability of the person for a job All participants receive identical resumes and job descriptions but the name on the resume is a male name for one group and a female name for the other group Lucia nds no difference in the ratings between the two groups What threat to internal validity should she be concerned about Demand Characteristics She should be concerned that the participants guess the manipulation in the study and were giving what they thought was the more socially acceptable answer 5 On the rst midterm exam in an introductory psychology class the grades are lower than Professor Mutola expected She suspects that multitasking is to blame She bans computers and cellphones from her class between the rst midterm and the second midterm When she compares the scores on the two exams for the people who had been using computers and cellphones she nds a signi cant improvement on the second exam What is the formal name for this type of design one group pretest posttest As described the only people Professor Mutola is studying are the multitaskers so it is one group She is using the rst exam as the pretest and the second as the posttest 6 Many threats to internal validity are corrected for by adding a comparison group Which of these is not one of the main threats to internal validity that occur even in designs with a clear comparison group maturation A comparison group can be used to control for maturation threats the changes in the treatment group that differ from those in the comparison group can be ascribed to the treatment 7 Which of the following is not one of the three most common threats to internal validity oor effects order effects selection effects design confounds Floor effects are a special case of weak manipulations and insensitive measures not one of the three most common threats 8 The students in 50 student introductory psychology class were randomly assigned to one of two review sessions each being taught with a different technique The next day every student got all 10 of the test questions correct What problem does Professor Zhao have in determining the better teaching technique for review sessions Ceiling effect because all the scores are squeezed together at the high end the effect of the independent variable couldn t be measured 9 What two types of validity in an experiment can observer bias threaten internal and construct Observer bias threatens internal validity because an alternative explanation exists and threatens construct validity because the ratings are inaccurate 10 Jared is conducting an experiment with ESP extrasensory perception training He begins with a pretest of his 40 participants and divides them into two groups based on their scores The participants with the 10 lowest scores are given extensive training on how to detect the signals The participants with the 30 highest scores are given no training Both groups are retested and the average score of the participants with the training improved while the average score of the participants without the training actually fell What threat to internal validity should Jared consider Regression The groups that was given training had an unusually bad performance on the pretest so was likely to regress upward in performance on the posttest even without training 11 Which of these is not a source of error variance selection effects can lead to a confounded experiment but would not increase variability within groups 12 Which of these is not a solution to individual differences as a source of within group variability Double blind studies can control for observer effects and demand characteristics but this wouldn t help with the contribution of individual differences to within group variability 13 What should be added to a double blind placebo control study to demonstrate that the placebo had an effect a no treatment no placebo group By including a group with no treatment or placebo and comparing that group to the placebo group the placebo effect is demonstrated 14 The Ranschburg effect in short term memory involves repeated items if they are close What is the independent variable repetition condition
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