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Chapter 4 – Research Methods

Chapter 4 – Research Methods. Different methods to answer different questions A. Does one factor cause another? The Scientific Method - obtain reliable information under controlled conditions. Example: Does psychotherapy cure snake phobia?

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Chapter 4 – Research Methods

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  1. Chapter 4 – Research Methods Different methods to answer different questions A. Does one factor cause another? The Scientific Method - obtain reliable information undercontrolled conditions

  2. Example: Does psychotherapy cure snake phobia? • Therapy vs. nothing => independent variable (IV) • Level of snake fear => dependent variable (DV)

  3. DV depends upon IV • How will we know if differences in snake fear are caused by therapy?

  4. Treatment of subjects (IV)- that which you are manipulating, systematically altering to see its effects • CONFOUND = any other difference between the groups

  5. If no confounds, only thing different between the groups is the IV, then high internal validity • Fairly sure that changes in the DV were due to IV

  6. How to increase internal validity? (make groups same except for IV) 1. Random assignment of subjects to groups Groups: Experimental vs. Control

  7. Experimental = receive treatment being tested • Control = comparison • How to divide sample into groups? • Random assignment*****

  8. Random assignment makes the 2 groups equivalent 2. No other differences between groups (“holding everything constant”) • These 2 factors decrease confounds, & increase internal validity

  9. Subjects/Who is in the experiment • Population = all people of interest • Sample = subset; those in the experiment

  10. Sample of convenience • Random sampling - everyone in population has an equal chance of being chosen

  11. Why random sampling? • Sample is representative of the population of interest • Can apply (“generalize”) results to population • Increases external validity

  12. External validity = generalizability • To other people, places, situations, etc.

  13. Key to Scientific Method = internal validity • Controls to ensure that IV -> DV • Rule out confounds • Random sampling is not critical • Increases external validity

  14. Problems: • Not always feasible or ethical • Studies are analogues – simulations of real life (low external validity)

  15. Advantage of Scientific Method • Cause and effect

  16. B. How strongly are two factors are related? Correlational designs • Longitudinal (how people change over time) • Naturalist observation (watch people in natural settings)

  17. Not a true experiment • No controls • Is there a numerical relationship between 2+ factors?

  18. Evaluating the outcome • A correlation coefficient indicates whether two variables are related - 1.0 to +1.0

  19. Magnitude: absolute value of #= strength of relation • Direction: sign + = as one increases, other increases - = as one increases, other decreases

  20. Relationships: • Positive • Negative • Curvilinear • None

  21. Problem • poor internal validity -> don’t know WHY things happen Reverse causality Third-variable problem Spurious relationships

  22. Advantages • easier, practical • ethical, real-life -> can have better external validity

  23. C. What can we learn from one subject? Three methods: • Case study • ABAB (Reversal) design • Multiple-baseline design

  24. Case study method - documenting behavior of one person

  25. Advantages: • Real life (somewhat higher external validity) • Suggests ideas • Practical, easy (one person) • Lots of information

  26. Disadvantages: • No controls/comparison (poor internal validity) • One subject not randomly selected (poor external validity)

  27. ABAB (Reversal) • Get baseline (A) • Introduce treatment (B) • Return to baseline (A) • Reintroduce treatment (B)

  28. Advantages: • More controlled than case study • Still requires only 1 subject

  29. Disadvantages: • One person = limited external validity • Sometimes unethical to withdraw treatment • If return to baseline, then no cure

  30. Multiple-baseline design = change several behaviors sequentially • Get baseline for all behaviors • Introduce treatment for first behavior • Then, treatment for second, etc. • Different treatments affect different behaviors

  31. Advantages: • More controlled than case study • Also requires only 1 subject • No withdrawal of treatment

  32. Disadvantages: • One person = limited external validity • Sometimes hard to disentangle effects on individual behaviors

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