Researchers conducting a randomized controlled trial can take several steps with regard to their sampling plan to enhance patient-centered evidence. One of these steps is to: make efforts to ensure that research samples reflect the full range of people who could benefit from (or be harmed by) the intervention. sample patients from a single site so that confounding contextual factors will be controlled. exclude patients who have characteristics that could confound the results. make efforts to sample in a manner that avoids heterogeneity of effects