Experimental and Quasiexperimental Method

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Experimental and Quasi-experimental Method

• September 16,2008

2
Learning Objectives

• Review APA reference list
• Gain some experience with experimental/quasi-exper
  imental designs.
• Learn how to use excel to analyze experimental
  data.
• Continue with introduction to writing a
  scientific paper.

3
References

• References
• Brown, W. M., Moore, C. (2002) Fluctuating
  asymmetry and romantic jealousy. Evolution and
  Human Behavior, 24, 113-117.
• Buss, D. M. Greiling, H. (1999). Adaptive
  individual differences. Journal of Personality,
  67(2), 209-243.
• Buss, D. M. (1991). Evolutionary personality
  psychology. Annual Review of Psychology, 42,
  459-491.
• Buss, D. M. (1997). Evolutionary foundations of
  personality. In Hogan, R., (Ed.), Handbook of
  personality psychology (pp. 317-344). London
  Academic Press.
• Buss, D. M. (2000).  The dangerous passion Why
  jealousy is as necessary as love and sex. New
  York Free Press.  

4
First Data Collection

• This time you will be the participants.
• We are going to run a quasi-experiment
• For now you do not need to know what are the
  conditions of the quasi-experiment.

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Instructions

• Go to http//www.thewritingpot.com/stroop/

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Instructions

• Go to http//www.thewritingpot.com/stroop/
• There are going to be a series of colored words.

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Instructions

• Go to http//www.thewritingpot.com/stroop/
• There are going to be a series of colored words.
• Your task is to hit the key which corresponds to
  the color of the word not what it says.

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Instructions

• Go to http//www.thewritingpot.com/stroop/
• There are going to be a series of colored words.
• Your task is to hit the key which corresponds to
  the color of the word not what it says.
• If you are ready go ahead and click on try
  experiment and then hit space bar.

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Stroop Effect Continued

• When you are done write down click on view
  results.
• Write down the average time for words which were
  different for the color and the amount of time it
  took for words which matched the color.
• Now repeat this entire process two more times.

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Microsoft Excel

• Open a new database.
• Write the following variable names congruent1,
  congruent2, congruent3,averagecongruent,
  noncongruent1, noncongruent2, noncongruent3,
  average congruent.
• Enter your scores from the experiment.

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Calculating a mean in Excel

• In the cell under average congruent type
  average(
• Type a2c2) or highlight the cells which contain
  your congruent data.
• In both cases you should have something like the
  following average(a2c2)
• Do the same for non congruent variables

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Were you strooped?
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Were you strooped?

• First you might want to plot mean stroop effects.
• To do this highlight the Average stroop scores
  for congruent and non-congruent
• In this case the ctrl button is helpful.
• First highlight one press control and highlight
  the other.
• Now click on insert graph
• Pick the bar graph
• Hit enter
• If your non-congruent stroop average score was
  higher than the average congruent score you were
  strooped

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Here are my scores
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Did your performance improve?

• How would we know?
• We could plot the learning curve for each
  condition.
• First highlight your congruent1, congruent2, and
  congruent3 scores.
• Now make a similar graph as before.

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My Improvement
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Was the Class Strooped?

• First we have to enter data.
• We already have the variable names in our
  database.
• Im going to call each of you one at a time.
• I want everyone to enter their classmates
  scores.
• I also want them to record each participants sex

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The Dataset
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Lets Do a T-Test

• On toolbar on top click Tools dropdown box will
  appear Choose Data Analysis then . . .
• Click t-test 2 samples assuming equal
  variance.
• Highlight data You should see a box with room to
  enter numbers for Variable 1 range and
  Variable 2 range.
• Hit Enter

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Are males more easily strooped?Our
quasi-experiment

• concept is the same
• comparing means
• analysis is a bit more complicated
• What do we need to do?

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Are males more easily strooped?

• concept is the same
• comparing means
• analysis is a bit more complicated
• What do we need to do?
• Hint- What are our independent variables

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Data Manipulation

• How do we calculate this difference score?
• First type ( in cell J2
• This creates a new variable.
• If you want you could name it stroop score.
• Highlight the noncongruent average
• (cell H2 if you followed my example)
• Follow that with a sign
• Then Highlight the congruent average
• (cell d2)
• The final product should read (H2-D2)

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Data Manipulation

• Now highlight cell J2
• There will be a little box on the border of that
  cell
• Click and drag it down to the end of the data
  set.
• This will give you the stroop score for each
  person.
• Positive numbers mean they were strooped negative
  or scores of zero means they were not.

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Now the Dependant Variable

• We have to sort the data set
• We need all the males in one section and all the
  female data on the other.
• Highlight all the data by clicking on the top
  left hand corner of the spreadsheet.
• Click on data
• Click on sort
• Sort by the column for the variable sex.

25
Lets Do a T-Test

• On toolbar on top click Tools dropdown box will
  appear Choose Data Analysis then . . .
• Click t-test 2 samples assuming equal
  variance.
• Highlight data You should see a box with room to
  enter numbers for Variable 1 range and
  Variable 2 range.
• This type highlight the difference scores for one
  of the sexes for variable 1 range and highlight
  the difference scores for the other sex variable
  2 range
• Hit Enter

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Assignment

• I want you to write up a methods and results
  section for the quasi-experiment we just
  conducted.
• See pages 367 and 368 in the Leary book.