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.