 The gold standard for assessing the effectiveness of interventions is the randomized clinical trial; yet patients who have a strong preference for one of the intervention conditions may decline to participate, which is a threat to external validity, or if randomized participate half-heartedly or drop out, threatening internal validity. Investigators will address this issue with a partially randomized preference trial in which patients with a strong preference are assigned to their preferred treatment i.e., intervention condition and those without a strong preference are randomized. This study design enables comparison of treatment outcomes among patients who receive their preferred treatment the desired real world situation and ascertainment of the effects of preferenceas well as the evaluation of treatment outcomes in a randomized trial. However, comparisons involving preference participants are subject to confounding, since patients who prefer a particular treatment may differ in ways that affect outcome. In analyses involving preference participants it is possible to reduce confounding substantially using covariate adjustment. Nevertheless, because residual confounding may be present, preference participant outcomes should be considered observational data. 