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

- 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