AP Psychology Homework
Statistics: Correlational Studies

While this assignment is not due for several days, I STRONGLY suggest you take a stab at it as soon as possible. If you decide to wait until the night before this is due to examine the questions, you will probably experience a significant amount of stress. To avoid this unnecessary trauma, please examine both questions tonight and come to class tomorrow with the questions you will (undoubtedly) have for me.

Question 1: Maxine (a graduate student in psychology) needed to come up with a topic for her thesis. She finally decided to examine the relationship between anxiety and cigarette smoking. Maxine distributed a packet of questionnaires to 300 randomly selected students who were enrolled at her university. Each packet contained two questionnaires .The first questionnaire simply asked each subject to indicate how many cigarettes he or she smoked (on average) each day. In order to limit demand characteristics, she also included questions about gardening habits, favorite TV shows, age, gender, internet service, etc. The second portion of her packet included a 50-item questionnaire that was designed to assess anxiety. Scores on the questionnaires could range from "0" (little or no anxiety) to "30" (very high anxiety).

Once she had scored all of the questionnaires, she separated the smokers from the non-smokers. She then randomly selected 30 packets from the group that smoked.

The following table lists the scores of the 30 students who smoke with respect to each of the questionnaires. ("S" stands for "Subject")

S

Anxiety Score

Cigarettes smoked daily

S

Anxiety Score

Cigarettes smoked daily

S

Anxiety Score

Cigarettes smoked daily

1

2

3

4

5

6

7

8

9

10

8

9

15

14

21

12

22

17

7

8

11

3

11

16

26

10

24

18

10

4

11

12

13

14

15

16

17

18

19

20

16

15

20

24

15

5

10

16

15

20

10

17

24

28

20

9

4

12

15

23

21

22

23

24

25

26

27

28

29

30

20

17

3

20

8

21

12

18

26

7

19

20

8

22

10

25

8

18

24

10

Your job is to:

  1. Construct a scatterplot to represent the correlation between smoking and anxiety.
  2. Describe (in general) the direction and strength of the correlation.
  3. Enter the data into your calculator and report the actual correlation coefficient.
  4. Is the value of "r" statistically significant at the .05 level?
  5. Provide two possible explanations for Maxine’s results (these two possibilities make it clear why we can’t infer causation from a correlational study).
  6. Identify a possible "3rd variable" that could impact both cigarette smoking and anxiety.

    7.  

    Question 2: Since Maxine already had the information (and was bored), she decided to see if there was a relationship between anxiety and gender.

    The following table lists the scores of the 30 students who smoke with respect to their anxiety scores and gender.

    Subject

    Gender

    Anxiety Score

    Subject

    Gender

    Anxiety

    Score

    Subject

    Gender

    Anxiety

    Score

    1

    2

    3

    4

    5

    6

    7

    8

    9

    10

    M

    M

    F

    F

    F

    F

    M

    M

    M

    F

    8

    9

    15

    14

    21

    12

    22

    17

    7

    8

    11

    12

    13

    14

    15

    16

    17

    18

    19

    20

    M

    M

    F

    F

    F

    M

    F

    M

    M

    M

    16

    15

    20

    24

    15

    5

    10

    16

    15

    20

    21

    22

    23

    24

    25

    26

    27

    28

    29

    30

    F

    M

    M

    F

    F

    M

    F

    M

    M

    F

    20

    17

    3

    20

    8

    21

    12

    18

    26

    7

     

    Your job is to:

  7. Construct a scatterplot to represent the correlation between gender and anxiety.
  8. Describe the direction and strength of the correlation.
  9. Enter the data into your calculator and report the actual correlation coefficient.
  10. Provide two possible explanations for Maxine’s results.
  11. OR be prepared to explain what the problem is in class tomorrow.


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