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					Applications Exercises           Research in Psych, 5e: Study Guide, Chapter 6                  6-1


Between or Within?
For each of the following, first identify the independent and dependent variables (in general
terms). Then decide whether it would be more appropriate to use a between-subjects design or a
within-subjects design, given the limited information presented for each study. Explain your
choice. If you think a between-subjects design is called for, decide whether equivalent groups
could be formed and if so, the best way to form them (random assignment or matching). If you
think matching is needed, identify a matching variable. If you think a within-subjects design is
called for, then make a recommendation about the type of counterbalancing to use.


1. In study of eyewitness memory, a researcher wishes to determine whether the accuracy of
   eyewitness memory can be influenced by the level of stress an eyewitness experiences.




2. In a cross-cultural study of prejudice, a researcher wished to know whether prejudices would
   develop earlier in life for Western (e.g., United States) or Eastern (e.g., China) cultures.




3. In a study on the sense of touch, blindfolded participants had to judge whether the apparatus
   touching their skin had two points or one. The researcher wished to determine if different
   areas of the skin (e.g., palm of the hand vs. small of the back) were differentially sensitive.




4. A cognitive psychologist interested in the development of memory studies (annually) the short-
   term memory capacity of the same 20 children as they grow from age 4 through age 8.




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Applications Exercises            Research in Psych, 5e: Study Guide, Chapter 6                       6-2




5. To determine whether there is universality to facial expressions of emotions, a researcher
   prepares pictures of people from three different cultures, each showing the same variety of
   expressions (e.g., smile, scowl). On a given trial of the study, a participant looks at a photo,
   then chooses a matching emotion from a list of ten different emotions.




6. A psychologist interested in maze wishes to learn whether learning is faster when the maze is
   run 10 times a day, once a day for ten 10 days, or twice a day for five days.




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Applications Exercises           Research in Psych, 5e: Study Guide, Chapter 6                   6-3


Answers

1. IV = stress levels experienced
   DV = eyewitness accuracy
   Between-subjects design: presumably there will be at least two levels of stress and a
   participant will witness some kind of event unexpectedly then have to report on it; having done
   this once, it would be impractical to have the same person do it again when experiencing a
   different level of stress.
   Equivalent groups: use random assignment if there is a large participant pool; otherwise, it
   might be wise to match the groups on their characteristic levels of anxiety, as determined by a
   test for anxiety tendencies.

2. IVs = culture and age
   DV = level of prejudice
   Between-subjects design: both independent variables are subject variables, thereby dictating
   a between-subjects approach; because the groups are inherently nonequivalent
   Equivalent groups: neither random assignment nor matching could be used to create
   equivalent groups (you will learn in Chapter 7, however, that a form of matching is often used
   in designs like this to reduce the degree of nonequivalency)

3. IV = area of the skin
   DV = judgment (one or two points)
   Within-subjects design: like most research in sensation and perception, this is a situation in
   which participating in one condition (palm being tested) won’t have much of an effect on being
   tested in the other condition (back), as long as counterbalancing is used properly; also, in this
   type of study it is important for each person to make a comparison between his or her palm
   and back.
   Counterbalancing: each position would probably be tested several times; either reverse
   counterbalancing or block randomization could be used; because there are only two positions
   being tested, another option would be to simply alternate from one to another.

4. IV = age
   DV = STM capacity
   Within-subjects design: by studying the same children every year, this is a longitudinal design.
   Counterbalancing: not relevant of course (unless the researcher has a time machine that
   would enable him or her to test a child first at age 8 then at age 6, etc.)

5. IV = cultures represented in the photos
   DV = accuracy of judging the emotion
   Within-subjects: it would be good to see if the same participant could accurately judge a
   particular emotion (e.g. sadness) when displayed in three different cultures.
   Counterbalancing: let’s say there are 21 photos - seven emotions shown for each of the three
   cultures; if each participant is tested once, partial counterbalancing would be used, probably
   by giving each participant a random sequence of the photos; if testing occurred more than
   once per participant, block randomization would probably be used (several consecutive
   random sequences of the 21 faces)

6. IV = maze running schedule
   DV = learning
   Between-subjects: once a rat has been tested in one of the three conditions, that rat “knows”
   the maze; rats should begin each of the three conditions in a state of maze ignorance.
   Equivalent groups: white rats are very similar genetically and cheap to buy or raise; random
   assignment will be fine here.




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