lesson 4 (expepsych)

• Internal validity


  An experiment is internally valid when the effects on the dependent variable are due to the independent variable
• Manipulation check


  Evaluates how well the experimenter manipulated the experimental situation, determines whether subjects followed directions and were appropriately affected by our treatments
• Threats to internal validity

  • Statistical conclusion validity
  • Selecting the wrong statistical test
  • Improperly using a statistical test
  • Drawing the wrong conclusions from a test
• External validity


  An experiment is externally valid when its finding can be extended to other situations and populations
• Requirements for an externally valid study

  • The experiment must be internally valid
  • The experimental findings can be replicated
• Generalizing data across subjects

  The findings can be extended to a larger group than the sample which is critical to the validity and usefulness of experimental findings
• Research significance


  A study achieves research significance when its findings clarify or extend knowledge gained from previous studies and raise implications for broader theoretical issues
• Extraneous variables are uncontrolled in real world settings


  They can modify the influence of our individual
• Aggregation


  The together and averaging of data to increase external validity, combining the results of experiments with different subjects and methodologies increases the generality and external validity of our findings
• Types of aggregation


  • Aggregation over subjects
  • Aggregation over stimuli or situations
  • Aggregation over trials or occasions
  • Aggregation over measures
• Meta-analysis


  Uses statistical analysis to combine and quantify data from many comparable experiments to calculate an average effect
• Nonreactive measurements


  Increase external validity by working to minimize reactivity in experiments, Develop unobtrusive measures: nonreactive measures
• Field experiment


  Manipulation of independent variable and observation in a natural setting
• Naturalistic observation


  Can validate or add substance to previously obtained laboratory findings
• Possible causes of a nonsignificant outcome

  • Confounding
  • Weak manipulation of the IV
  • Inconsistent or flawed procedures
  • Ceiling and floor effects
• Accept the outcome, don't reframe your result as "almost significant"