RESEARCH DESIGNS AND SOURCES OF INVALIDITY
Pre-Experimental and True Experimental Designs(1)
 
True Experimental Designs Pre-Experimental Designs
Pre/Post test control group Solomon Four Group Post-test only control group  One-shot case study One group Pre/Post test Static group comparison
Internal Validity
History + + + - - +
Maturation + + + - - ?
Testing + + + - +
Instrumentation + + + - +
Regression + + + ? +
Selection + + + - + -
Mortality + + + - + -
Contamination + + + - -
External Validity
Testing and X - + + -
Selection and X ? ? - - -
Reactive Arrangements ? ? ? ?
Multiple X interference
 
RESEARCH DESIGNS AND SOURCES OF INVALIDITY
Quasi-Experimental Designs(2)
 
Quasi-Experimental Designs
Time Series Equivalent Time Samples Equivalent Materials Samples Non-equivalent Control Group Counterbalanced Design Separate Sample Pre-test Post-test
Internal Validity
History - + + + + -
Maturation + + + + + -
Testing + + + + + +
Instrumentation ? + + + + ?
Regression + + + ? + +
Selection + + + + + +
Mortality + + + + + -
Contamination + + + - ? -
External Validity
Testing and X - - - - ? +
Selection and X ? ? ? ? ? +
Reactive Arrangements ? - ? ? ? +
Multiple X interference - - -
1. A plus sign (+) indicates that the threat to validity is controlled. A minus sign (-) indicates a definite weakness in this design concerning the threat to validity. A question mark (?) indicates a possible source of concern; and a blank indicates that the threat is not relevant.

2. A plus sign (+) indicates that the threat to validity is controlled. A minus sign (-) indicates a definite weakness in this design concerning the threat to validity. A question mark (?) indicates a possible source of concern; and a blank indicates that the threat is not relevant.