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? 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 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