Introduction to Experimental Research

1
Chapter 5

• Introduction to Experimental Research

2
John Stuart Mills Canons of Causation

• Method of Agreement
• Method of Difference
• Joint Methods of Agreement and Difference
• Method of Concomitant Variation

3
Essential Features

• Independent variables (IV)
• Minimum of two levels
• Varieties of IVs
• Situational
• Task
• Instructional
• Control vs. experimental groups

4
Essential Features (cont.)

• Controlling extraneous variables
• Extraneous variables (EV)
• Confounding variables
• Measuring Dependent Variables (DV)
• Manipulated vs. participant variables
• Note any given construct could be an IV, DV or EV

5
Validity

• Statistical conclusion validity proper use of
  statistics (including proper conclusions drawn)
• Construct validity adequacy of operational
  definitions
• External validity generalizability
• Internal validity methodologically sound and
  confound free

6
Threats to Internal Validity

• Pre-post studies
• History and Maturation
• Regression to the mean
• Testing and instrumentation
• Participant problems
• Selection
• Attrition