A Matched Observational Study

Abstract

As a prelude to several chapters describing the construction of a matched control group, the current chapter presents an example of a matched observational study as it might (and did) appear in a scientific journal. When reporting a matched observational study, the matching methods are described very briefly in the Methods section. In more detail, the Results section presents tables or figures showing that the matching has been effective in balancing certain observed covariates, so that treated and control groups are comparable with respect to these specific variables. The Results section then compares outcomes in treated and control groups. Because matching has arranged matters to compare ostensibly comparable groups, the comparison of outcomes is often both simpler in form and more detailed in content than it might be if separate adjustments were required for each aspect of each outcome. Treated and control groups that appear comparable in terms of a specific list of measured covariates – groups that are ostensibly comparable – may nonetheless differ in terms of covariates that were not measured. Though not discussed in the current chapter, the important issue of unmeasured covariates in this example is discussed in Part III.