The Use of Qualitative Evaluation Methods to Test Internal Validity

Abstract

Since the late 1970s, qualitative research methods have gained recognition for their potential contribution to the evaluation of health promotion and educationprograms. Today, the issue is no longer whether to use quantitative or qualitative methods, but rather, how they can be combined to provide more complete assessments of the impact of a program. Each method is based on different yet complementary assumptions and each method has certain strengths that can be used to compensate for the limitations of the other. This article illustrates how qualitative and quantitative methods were combined in the evaluation of a health promotion program conducted in 23 rubber-producing plants in the United States. The qualitative case study and monitoring data were used to complement the quantitative study through the testing of threats to internal validity, and through the detection of a Type III error, that is, the inadequate implementation of the primary program intervention. In experimental and quasi-experimental evaluations it is recommended that selected in-depth case studies of both experimental and control sites be conducted Such case studies are essential for answering the question of why program activities were or were not carried out.