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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 Different methods to answer different questions A. Does one factor cause another? The Scientific Method - obtain reliable information undercontrolled conditions
Example: Does psychotherapy cure snake phobia? • Therapy vs. nothing => independent variable (IV) • Level of snake fear => dependent variable (DV)
DV depends upon IV • How will we know if differences in snake fear are caused by therapy?
Treatment of subjects (IV)- that which you are manipulating, systematically altering to see its effects • CONFOUND = any other difference between the groups
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
How to increase internal validity? (make groups same except for IV) 1. Random assignment of subjects to groups Groups: Experimental vs. Control
Experimental = receive treatment being tested • Control = comparison • How to divide sample into groups? • Random assignment*****
Random assignment makes the 2 groups equivalent 2. No other differences between groups (“holding everything constant”) • These 2 factors decrease confounds, & increase internal validity
Subjects/Who is in the experiment • Population = all people of interest • Sample = subset; those in the experiment
Sample of convenience • Random sampling - everyone in population has an equal chance of being chosen
Why random sampling? • Sample is representative of the population of interest • Can apply (“generalize”) results to population • Increases external validity
External validity = generalizability • To other people, places, situations, etc.
Key to Scientific Method = internal validity • Controls to ensure that IV -> DV • Rule out confounds • Random sampling is not critical • Increases external validity
Problems: • Not always feasible or ethical • Studies are analogues – simulations of real life (low external validity)
Advantage of Scientific Method • Cause and effect
B. How strongly are two factors are related? Correlational designs • Longitudinal (how people change over time) • Naturalist observation (watch people in natural settings)
Not a true experiment • No controls • Is there a numerical relationship between 2+ factors?
Evaluating the outcome • A correlation coefficient indicates whether two variables are related - 1.0 to +1.0
Magnitude: absolute value of #= strength of relation • Direction: sign + = as one increases, other increases - = as one increases, other decreases
Relationships: • Positive • Negative • Curvilinear • None
Problem • poor internal validity -> don’t know WHY things happen Reverse causality Third-variable problem Spurious relationships
Advantages • easier, practical • ethical, real-life -> can have better external validity
C. What can we learn from one subject? Three methods: • Case study • ABAB (Reversal) design • Multiple-baseline design
Case study method - documenting behavior of one person
Advantages: • Real life (somewhat higher external validity) • Suggests ideas • Practical, easy (one person) • Lots of information
Disadvantages: • No controls/comparison (poor internal validity) • One subject not randomly selected (poor external validity)
ABAB (Reversal) • Get baseline (A) • Introduce treatment (B) • Return to baseline (A) • Reintroduce treatment (B)
Advantages: • More controlled than case study • Still requires only 1 subject
Disadvantages: • One person = limited external validity • Sometimes unethical to withdraw treatment • If return to baseline, then no cure
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
Advantages: • More controlled than case study • Also requires only 1 subject • No withdrawal of treatment
Disadvantages: • One person = limited external validity • Sometimes hard to disentangle effects on individual behaviors