M7: Threats to External Validity

Question 1

What are the 2 categories of
External Validity?

Answer 1

1. Population Validity
2. Ecological Validity

Question 2

What is Population Validity?

Answer 2

The extent to which findings from a sample can be generalized to a broader population

Question 3

What is Ecological Validity?

Answer 3

The extent to which research
emulates the real world

Question 4

What are the threats to external validity?

Answer 4

1. Reactive/interactive effects of testing
2. Interaction of Selection Bias & the Experimental Treatment
3. Multiple Treatment Interference

Question 5

How do threats to external validity arise?

Answer 5

Arise when experimenters draw incorrect generalizations from the sample data to other persons, other settings, and past or future situations

Question 6

What is the reactive/interactive
effects of testing?

Answer 6

The pretest may make the participant more aware of or sensitive to the upcoming treatment

• As a result, treatment is not as effective w/o the pretest

Question 7

How is the Interaction of Selection Bias & the Experimental Treatment a threat to external validity?

Answer 7

When a group is selected on some characteristics, the treatment may work only on groups possessing that characteristic

• E.g., gender, age, sport, nationality

Question 8

How is multiple treatment interference a threat to external validity?

Answer 8

When participants receive more than one treatment, the effects of previous treatments may influence subsequent ones

Question 9

How can we control threats to external validity?

Answer 9

Selecting participants, treatments, experimental situation, and tests to represent a broader population

• Random selection

Researcher might restrict claims about groups to which the results cannot be generalized

• Conduct additional experiments with groups with different characteristics