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Chapter 13

Chapter 13. Inferential Data Analysis. 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. Example 1. Why do butterflies and moths have eye spots?.

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Chapter 13

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  1. Chapter 13 Inferential Data Analysis Conducting & Reading Research Baumgartner et al

  2. 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 Conducting & Reading Research Baumgartner et al

  3. Example 1 Conducting & Reading Research Baumgartner et al

  4. Why do butterflies and moths have eye spots? 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). Conducting & Reading Research Baumgartner et al

  5. 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 Conducting & Reading Research Baumgartner et al

  6. 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. Conducting & Reading Research Baumgartner et al

  7. What are the independent and dependent variables? • Independent: Chamber selected • Dependent: Amount of time spent there. Conducting & Reading Research Baumgartner et al

  8. 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 Conducting & Reading Research Baumgartner et al

  9. Alternative hypotheses, controls? • Lighting in chambers • Time of day • Motivation (food deprivation) • Different or same species? Conducting & Reading Research Baumgartner et al

  10. Example 2 Conducting & Reading Research Baumgartner et al

  11. 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) Conducting & Reading Research Baumgartner et al

  12. Research hypothesis: There is no difference in the effectiveness of the two types of aspirin • Experiment: • Test clearance of each type of aspirin one hour after it is given • Sample: • N=10 subjects Conducting & Reading Research Baumgartner et al

  13. 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 Conducting & Reading Research Baumgartner et al

  14. What are the independent and dependent variables? • Independent: • Type of aspirin • Dependent: • Amount of aspirin in urine 1-hour later Conducting & Reading Research Baumgartner et al

  15. 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 Conducting & Reading Research Baumgartner et al

  16. Alternative hypotheses, controls? • Differences in subjects body composition • Differences in subjects eating/drinking habits • Genetic differences in pharmacological response to aspirin Conducting & Reading Research Baumgartner et al

  17. Example 3 Conducting & Reading Research Baumgartner et al

  18. Duncker’s Candle Problem • 2 volunteers to leave room • Haven’t had class in cognitive psychology Conducting & Reading Research Baumgartner et al

  19. Research hypothesis: It will take longer for subjects who are given tacks in the box to solve the problem. • Experiment: • Test length of time it takes subjects to solve the problem. • Sample: • N=20 subjects Conducting & Reading Research Baumgartner et al

  20. 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 Conducting & Reading Research Baumgartner et al

  21. What are the independent and dependent variables? • Independent: • Location of tacks • Dependent: • Amount of time to solve problem Conducting & Reading Research Baumgartner et al

  22. 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 Conducting & Reading Research Baumgartner et al

  23. Alternative hypotheses, controls? • Attitude of researcher as box, tacks, candle are presented • Differences in subjects educational background/IQ • Differences in subjects age/gender Conducting & Reading Research Baumgartner et al

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