Exam 2 PS 306, Fall 20031. Dr. Melody Brooks is interested in assessing whether or not people eat more when they are anxious. Shebrings her participants into the lab one at a time and places a bowl of 30 salted peanuts in front of them,explaining that the participant should feel free to eat as many peanuts as she or he would like. Dr. Brooksthen has half the participants fill out an ominous-looking consent form, absolving her of all liability shouldthe experiment result in permanent damage to the participant. She then tells these participants that they willreceive a series of painful electric shocks (though there will be “no permanent tissue damage”), todetermine their tolerance for pain. The other half of the participants is given a standard consent form thatsimply describes the experiment and asks for the participant’s cooperation. Dr. Brooks then tells this groupthat they will be serving as a control group for an experiment and will have to wear a shock electrode andreceive a mild electric shock, but that it will only feel like a mild tingle. (Dr. Brooks might well have seenthe same movie you saw at the beginning of the semester.) Neither group actually receives a shock, withthe threat of the different shock levels intended to create different anxiety levels. At the conclusion of theexperiment, Dr. Brooks is surprised to see that there is no difference between the two groups in terms ofpeanuts eaten (M for the anxious group = 29.8, M for the non-anxious group = 29.5). What advice wouldyou give Dr. Brooks about her experiment? Because you want to make the experiment more powerful,would you suggest using a repeated measures (within subjects) design? [10 pts]First of all, given the deceptive nature of this study, I don’t think that one couldreadily change it to a repeated measures design. That is, given that the participant isnot actually shocked, you wouldn’t be able to deceive them when introducing thesecond condition (this time I’m really, really, really going to shock you!). Next, youshould note that the means don’t differ much and that they are both quite high(people typically eating all of the nuts), which typifies a ceiling effect. Thus, youshould probably run the experiment again, but with more than 30 nuts in the bowl. Ithink that you should also consider a control group in which the participantsexperience no undue anxiety (i.e., no threat of shock at all).2. Dr. Nick O. Thyme was interested in studying the effects of practice on performance on video games thatinvolve a great deal of eye-hand coordination. He decides to conduct a two-factor mixed design, withamount of practice (3 hours, 6 hours, 12 hours) as the between (independent groups) factor and input device(keyboard, mouse, joystick) as the within-subjects (repeated measures) factor. He uses the score on a novelvideo game as the dependent variable. [15 pts]a. Given the design specified above, if Dr. Thyme wants to have a minimum of 20 scores per cell(condition), tell him how many participants he would need to run.This study would involve a 3x3 mixed design. To completely counterbalance therepeated factor (3 levels of input device) would require 6 orders. Because 24 is thefirst multiple of 6 to exceed 20, I would need to run 24 participants in each of thethree levels of the between factor (practice), for a total of 3 x 24 = 72 participants.b. Briefly describe a good procedure that Dr. Thyme might use to conduct his study.First of all, I would want to include a 0 hours of practice control group (todetermine how well people would perform if they had no practice at all). If I wereconstrained to 3 levels of the practice factor, I would use 0, 6, and 12 hours ofpractice. I would randomly assign participants to the amount of practice factor.Because those practice times are too great to administer all at once, I would haveparticipants practice in blocks of .5 hour (for example) on each input device, with a10-minute break between practice sessions and with 3 sessions per day (one sessionon each input device). I would also use random orders of devices for each practicesession. That would mean that the participants in the 12-hour practice group, forexample, would have to practice over a period of 8 days.At the end of the practice period, I would test each participant on each input device,using one of the 6 orders: KMJ, KJM, JKM, JMK, MJK, MKJ. Each order wouldbe used equally often, so each order would be used 4 times within each of the levelsof the practice factor.c. Suppose that he runs the study and finds no main effects or interaction. What would you advise him tochange in his study to make it more powerful? Do you think it would help if he were to run the study as acompletely within (repeated measures) design?Of course, one approach would be to increase n (sample size). Beyond thatapproach, I would consider increasing treatment effects by using even greaterpractice times (0, 12, 24, 48 hours) and possibly other input devices. I may also lookto see if there are ceiling or floor effects, which might lead me to use a more difficultgame or an easier game. I would also work to decrease variability, possibly by usingmore similar participants (all with very little video game experience, or all with agreat deal of video game experience, or all athletes with good eye-hand coordination,etc.). I would also work to ensure that the testing room was well isolated to minimizedistractions, make sure that the instructions were very clear, etc.3. A major research technique in the field of behavioral genetics is to breed animals selectively on the basisof particular characteristics exhibited by the animals and then to observe the relative performance of theoffspring. Suppose that an experiment is conducted in which three strains of rats are to be compared. Onestrain was obtained by selectively breeding rats who performed exceptionally well in a maze-learning task(the “bright” rats); a second strain was obtained by selectively breeding rats who performed quite poorly onthe same task (the “dull” rats); and a third strain consisted of rats who were bred without regard for maze-learning performance (the “mixed” rats). One group from each strain was raised under “enriched”conditions, and a second group was raised under “impoverished” conditions. The enriched environmentconsisted of a large cage containing objects for the animals to play with; the impoverished environmentconsisted of a similar cage