Threats to the Internal Validity of Experimental and Quasi-Experimental Research in Healthcare

• Published in: Journal of health care chaplaincy Vol. 24; no. 3; pp. 107 - 130
• Main Authors: Flannelly, Kevin J., Flannelly, Laura T., Jankowski, Katherine R. B.
• Format: Journal Article
• Language: English
• Published: United States Routledge 01-07-2018; Taylor & Francis Ltd
• Subjects: Design of experiments; Diagrams; experimentation; Health care; Internal validity; Maturation; methodology; Mortality; Quasi-experimental methods; quasi-experiments; Research design; Research methodology; Validity; internal validity; research design; experimentation; methodology; quasi-experiments
• ISSN: 0885-4726; 1528-6916
• DOI: 10.1080/08854726.2017.1421019

The article defines, describes, and discusses the seven threats to the internal validity of experiments discussed by Donald T. Campbell in his classic 1957 article: history, maturation, testing, instrument decay, statistical regression, selection, and mortality. These concepts are said to be threats to the internal validity of experiments because they pose alternate explanations for the apparent causal relationship between the independent variable and dependent variable of an experiment if they are not adequately controlled. A series of simple diagrams illustrate three pre-experimental designs and three true experimental designs discussed by Campbell in 1957 and several quasi-experimental designs described in his book written with Julian C. Stanley in 1966. The current article explains why each design controls for or fails to control for these seven threats to internal validity.