Lecture 8: Quantitative Research

Question 1

Internal Validity

Answer 1

• Researchers ability to claim that any change in an outcome is the result of a treatment or intervention (i.e. manipulation of the independent variable) and not a result of other factors.
• Confidence that changes in the dependent variable are actually caused by the independent variable.

Question 2

External Validity

Answer 2

The extent to which the results of a study can be generalizable to the population.

Question 3

Threats to Internal Validity

Answer 3

Threats Related to:

1. Experimental Procedure
   - Testing
   - Instrument accuracy
2. Threats related to the treatment or manipulation
   - Diffusion of treatments
   - Halo Effect
3. Threats related to participants
   - Maturation
   - History
   - Regression
   - Selection Bias
   - Experimental drop-out
   - Placebo
   - Hawthorne effect

Question 4

Testing

Answer 4

Practice Effect
Participants might become familiar with the test, and this might influence future performances.

Ways to reduce the effects of testing:
-Increase time period between testing or give practice opportunities

Question 5

Instrument accuracy

Answer 5

• Validity and reliability of the instrument/questionnaire.
  i. e. the DV could change as a results of inaccurate calibration of a machine, inappropriate use of the instrument or different techniques used in the first and follow up measures.
• Ways to reduce the effects of instrument accuracy:
• Have the same person complete the measurements overtime, using the same machine and calibration.