chapter 12 conducting & reading research baumgartner et al chapter 13 inferential data analysis
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Chapter 12Conducting & Reading
ResearchBaumgartner et al
Chapter 13
Inferential Data Analysis
Chapter 12Conducting & Reading
ResearchBaumgartner et al
Review of statistical tests
• One sample t test• Two independent samples t test• Two dependent samples t test• ANOVA• One-way Chi-Square Test• Two-way Chi-Square Test
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Example 1
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Ferguson, Douglas C., Chuck E. Harp, Paul A. Opler, Richard S. Peigler, Michael Pogue, Jerry A. Powell, and Michael J. Smith. 1999. Moths of North America. Jamestown, ND: Northern Prairie Wildlife Research Center Home Page. http://www.npwrc.usgs.gov/resource/distr/lepid/moths/mothsusa.htm (Version 12DEC2003).
Why do butterflies and moths have eye spots?
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Research hypothesis: Eye spots are a defense against moth-eating birds.
• Experiment:– Test effect of exposure to eye-spot
patterns on behavior of moth-eating birds.
• Sample:– N=16 moth-eating birds
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• Method:– Test in a 2 chamber enclosure,
separated by a partition with a doorway. Birds are free to roam from chamber to chamber.
– Chamber 1 has plain walls, chamber 2 has eye-spot patterns painted on the walls.
– Birds are tested one-at-a-time by placing in the doorway in the center.
– Each bird left in box for 60 minutes.– Amount of time spent in each
chamber is recorded.
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What are the independent and dependent variables?
• Independent: Chamber selected
• Dependent: Amount of time spent there.
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What statistical test do we use?
• One sample t-test• H0: Birds show no preference for
either chamber– H0: µ = 30 (for room with spots)
• HA: Eye patterns affect behavior, but will they show avoidance or attraction?– HA: µ ne 30 (2-tailed test)
• Go to SPSS file to analyze
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Alternative hypotheses, controls?
• Lighting in chambers• Time of day• Motivation (food deprivation)• Different or same species?
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Example 2
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Pharmacology example
• Assess effectiveness of new drug by noting concentration in blood and/or urine certain time points after giving
• Want to compare two types of aspirin (A and B)
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• Experiment:– Test clearance of each type of aspirin
one hour after it is given
• Sample:– N=10 subjects
Research hypothesis: There is no difference in the effectiveness of the
two types of aspirin
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• Method:– Randomly assign half the subjects to
receive aspirin A first and the other half to receive aspirin B
– Give same dosage of assigned aspirin to each subject
– Test amount of aspirin in urine 1 hour later
– One week later, after aspirin has cleared system, test each subject with the other aspirin
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What are the independent and dependent variables?
• Independent:– Type of aspirin
• Dependent:– Amount of aspirin in urine 1-hour later
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What statistical test do we use?
• Two dependent samples sample t-test• H0: No difference in amount of drug in
system– H0: µA - µB = 0
• HA: There is a difference in amount of drug in system– HA: µA - µB ne 0 (2-tailed test)
• Go to SPSS file to analyze
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Alternative hypotheses, controls?
• Differences in subjects body composition
• Differences in subjects eating/drinking habits
• Genetic differences in pharmacological response to aspirin
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Example 3
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Duncker’s Candle Problem
• 2 volunteers to leave room– Haven’t had class in cognitive
psychology
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• Experiment:– Test length of time it takes subjects
to solve the problem.
• Sample:– N=20 subjects
Research hypothesis: It will take longer for subjects who are given
tacks in the box to solve the problem.
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• Method:– Randomly assign half the subjects to
get tacks in the box and half to get tacks out of the box
– Measure how much time it takes each subject to solve the problem
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What are the independent and dependent variables?
• Independent:– Location of tacks
• Dependent:– Amount of time to solve problem
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What statistical test do we use?
• Two independent samples t-test• H0: No difference between people
who get tacks in box or out of box– H0: µ1 - µ2 = 0
• HA: The group who gets the tacks in the box takes more time to solve– HA: µ1 - µ2 > 0 (1-tailed test)
• Go to SPSS file to analyze
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Alternative hypotheses, controls?
• Attitude of researcher as box, tacks, candle are presented
• Differences in subjects educational background/IQ
• Differences in subjects age/gender