Document Type

Article

Publication Date

1975

Publication Citation

4 Sociological Methods & Research 101 (1975)

Abstract

This paper delimits and explicates threats to external validity particularly problematic in evaluation research. Five categories of factors are discussed: selection effects, measurement effects, confounded treatment effects, situational effects, and effects due to differential mortality. The paper focuses on pointing up specific ways in which each of the factors threaten generalizability and possible solutions to the methodological problems presented.

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