NCJ Number
38444
Date Published
1976
Length
0 pages
Annotation
THIS PAPER DELIMITS AND EXPLICATES THREATS TO EXTERNAL VALIDITY PARTICULARLY PROBLEMATIC IN EVALUATION RESEARCH.
Abstract
FIVE CATEGORIES OF FACTORS ARE DISCUSSED: SELECTION EFFECTS, MEASUREMENT EFFECTS, CONFOUNDED TREATMENT EFFECTS, SITUATIONAL EFFECTS, AND EFFECTS DUE TO DIFFERENTIAL MORTALITY. THE SPECIFIC WAYS IN WHICH EACH OF THESE FACTORS THREATEN GENERALIZABILITY ARE POINTED OUT AND POSSIBLE SOLUTIONS TO THE METHODOLOGICAL PROBLEMS ARE PRESENTED. REFERENCES ARE INCLUDED. (AUTHOR ABSTRACT)