Social Psychology
Instructor:  Susan Boland

Case Study 1.5 

·          This case study assignment requires that you apply information from lecture and from Chapter 2 of the textbook.  Read the case study carefully and answer the six questions in detail.  Follow the instructions for case study assignments in the course handout booklet.  A copy of the instructions is also on reserve in the library and on my web-page http://www.lhup.edu/sboland

·          Avoid quoting directly from the textbook -- write using your own words.  Information taken from the text, even if rewritten in your own words, must be credited to or cited to the textbook authors or to lecture.  See the full instructions for more information about citing the text as a reference. 

·          If you have any questions regarding this assignment please ask. 

Case Study 1.5 (30 points):  Can You Hear Me Now? 

     Two psychology students, Janet and Dave are required to conduct a study for the final project in their research methods course.  They are both interested in the effect of noise on stress levels.  Here are their stories.

     Janet has a friend who lives near a large metropolitan airport and who frequently complains about how much noise the jets make as they fly by.  Janet wonders if people living in such noisy environments experience more stress reactions than people who live in quieter surroundings.  She identifies two neighborhoods to include in her study.  One neighborhood is located within one mile of the airport the second neighborhood is five miles away from the airport.  Using telephone directories, she mails short surveys to a random selection of addresses in each subdivision.  In her survey she asked questions about physical, emotional and cognitive signs of stress such as the occurrence of headaches, feelings of anxiety or nervousness, irritability, and trouble concentrating.   She called each home to tell the residents about the purpose of the survey and to ask for their cooperation in completing the survey.  After waiting three weeks, she has received approximately 65% of the completed surveys with a nearly equal number of surveys coming from the two neighborhoods.

      Dave decides to take a different approach in his study.  He wants to test the hypothesis that noise increases stress and thus interferes with cognitive functioning.  He conducted the study in a small laboratory in which he could control the noise levels.  He recruited volunteers to participate in the study by posting a sign-up sheet by the mailroom in his dorm.  When volunteers came to the lab, Dave sat them in a small room and had them work on solving anagrams (scrambled words).  The people were randomly assigned to one of two conditions.  In the first condition, a buzzing sound at 90 decibels (approximately as loud as a lawn mower) was piped into the room.  In the second condition, the same buzzing sound was set at 40 decibels (approximately the loudness of a humming refrigerator).  All other environmental conditions (e.g., lighting, amount of space, the anagrams) were kept constant across conditions.  After the participants worked in the room for 15 minutes, they were debriefed.  Dave compared the number of anagrams correctly solved by participants in the two noise conditions.

   1)      One of the studies uses a correlational design and one uses an experimental design. First briefly
         describe each type of research design.  Next identify each study idea as correlational or
         experimental.  Finally, explain the basis for your identification.  In other words, explain what makes
         one of the study ideas a correlational design and the other an experimental design.

  2)      a) What results do you predict Janet will find in her study? What type of relationship would you
             expect Janet to find between the variables, proximity to the airport and stress?  Do you think the
             relationship would be positive or negative? Explain your answer. 

      b)  If Janet discovered a strong relationship between proximity to the airport and stress symptoms, can
           she conclude that the amount of noise causes stress symptoms?  Explain your answer.  Give at least
           one alternative explanation for a relationship between proximity to the airport and reported stress
           symptoms. 

3)      a)  In your own words, define independent variable.  What is the independent variable in the
     experimental study? How is the variable manipulated in the study?   

      b) What is the dependent variable in the experiment? You should define the term dependent variable in
          your answer.  How is the dependent variable measured?

       c) Suggest either a different way to manipulate the independent variable OR a different way to
           measure the dependent variable.  That is, suggest a change in either the experiment's  independent
           or dependent variable.  

4)      a) Dave randomly assigned volunteers to the noise conditions.  What is random assignment?   Describe a specific procedure Dave could use to randomly assign the participants.

       b) Did Dave use a random sample of participants in his study (assume the population of interest is
           students at Dave's college)?  Define random sample and explain why Dave's sample does or does
           not meet the requirements.

 5)      a)  What is internal validity?  How does random assignment contribute to good internal validity? 
            (One way to approach this question is to think what would happen if Dave hadn't used random
            assignment.  Suppose he let participants choose for themselves whether to be in the 90 or 40-
            decibel room.)   

      b)  Besides random assignment, what else did Dave do in his study that improved internal validity? 

6)      Compare Janet and Dave's studies.  Describe one advantage (strength) and one disadvantage (weakness) of the Janet's study. Also describe one advantage and one disadvantage of Dave's study.  If you had to choose one of these studies as being better, which would you choose and why?