More on Experimental Design

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More on Experimental Design

• Completely Randomized Design
• Block Design

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Layoffs and Survivor Guilt

• Workers who survive a layoff of other employees
  at their location may suffer from survivor
  guilt. A study of survivor guilt and its effects
  used as subjects, 120 students who were offered
  an opportunity to earn extra credit by doing
  proofreading. Each subject worked in the same
  cubicle as another student, who was an accomplice
  of the experimenters. At a break midway through
  the work, one of the three things happened

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Layoffs and Survivor Guilt

• Treatment 1 The accomplice was told to leave it
  was explained that this was because she performed
  poorly.
• Treatment 2 It was explained that unforeseen
  circumstances meant there was only enough work
  for one person. By chance the accomplice was
  chosen to be laid off.
• Treatment 3 Both students continued to work
  after the break.

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Experiment Diagram
Accomplice fired because he/she did poorly
Group 1 40 Subjects
Compare performance after the break
Group 2 40 Subjects
Random Assignment
Accomplice randomly fired
Group 2 40 Subjects
Both continue to work
5
Soybeans Blocking

• The soil type and fertility of farmland differ by
  location. Because of this, a test of the effect
  of two tillage types and three pesticide
  applications on soybeans yields uses small fields
  as blocks. Can you diagram this experiment?

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Soybeans Blocking
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Matched Pairs Designs

• Design an experiment to compare old and new
  waterproofing treatments on the boots of
  volunteers.

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Matched Pairs Designs

• Design an experiment to compare the seated
  resting heart rate and standing heart rate of you
  and your classmates.

9
Statistical Significance

• An observed effect so large that it would rarely
  occur by chance is called statistically
  significant.
• E.g. Bottled Water versus Tap Water
• Was 60 correct significant in that case.