Research design I

1
Research design I

• The independent variable
• Cause and effect

2
John Stuart Mill (1874)

• Canons of causation
• Method of agreement
• Method of difference
• Joint methods of agreement and difference
• Method of concomitant variation

3
Manipulating the independent variable Strategies

• Presence vs. absence
• Amount of variable
• Type of variable
• Importance of a comparison condition

4
Tactics for manipulation

• Conceptual IV vs. manipulated IV
• Check the literature
• Modify existing procedures
• Choose among available options
• Create a new manipulation

5
Another strategic analysis

• Manipulate instructions
• Manipulate events
• Problematic approaches
• Measured manipulation
• Internal analysis of the data

6
Checking back

• Do my manipulations really represent the
  conceptual IV?
• Will my manipulations affect the DV? How?
• 1. Different manipulation techniques should
  produce similar results.
• 2. The technique should produce expected outcomes.

7
More checking the IV

• Manipulation checks
• After the DV measure, to avoid interference, by
  interview, test, or measurement.

8
Selecting Ivs

• Number of IVs
• Avoid Whynot variables
• Consider interactions