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

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.

Studying Associations in Health Care Research.

This article discusses some of the types of relationships observed in healthcare research and depicts them in graphic form. The article begins by explaining two basic associations observed in chemistry and physics (Boyles' Law and Charles' Law), and illustrates how these associations are similar to curvilinear and linear associations, respectively, found in healthcare. Graphs of curvilinear associations include morbidity curves and survival and mortality curves.

Independent, dependent, and other variables in healthcare and chaplaincy research.

This article begins by defining the term variable and the terms independent variable and dependent variable, providing examples of each. It then proceeds to describe and discuss synonyms for the terms independent variable and dependent variable, including treatment, intervention, predictor, and risk factor, and synonyms for dependent variable, such as response variables and outcomes. The article explains that the terms extraneous, nuisance, and confounding variables refer to any variable that can interfere with the ability to establish relationships between independent variables and dependent variables, and it describes ways to control for such confounds.

Operational definitions in research on religion and health.

This article summarizes the historical development of operational definitions and discusses their application to research on religion and health, and their importance for research, in general. The diversity of religious concepts that have been operationalized is described, as well as the development of multi-dimensional self-report measures of religion specifically designed for use in health research. The operational definitions of a variety of health concepts are also described, including the development of multi-dimensional self-report measures of health.

Fundamentals of measurement in health care research.

This article discusses levels of measurement and their application to research and practice in health care. The concept of levels of measurement was codified in a seminal article by S. S.