In epidemiology, an<unk>  to<unk>  <unk>  is an<unk>  based on the initial<unk> ment intent, not on the<unk> ment eventually administered. The<unk>  includes all patients randomized to a therapy irrespective of protocol deviations, discontinuation of study drug, drug administration errors, cross-over to another strategy, or withdrawal from the study by the subject.  For example, in a trial comparing medical therapy to angioplasty for coronary artery disease, those patients who were initially randomized to medical therapy but who crossed-over to receive an angioplasty instead due to a failure of medical therapy are analyzed as part of the medical therapy cohort. This form of<unk>  differs significantly from a per protocol (PP)<unk>  in which only those subjects are included who actually received study drug as specified in the study protocol.
Intention to treat analysis
Block design
Surrogate endpoint
Evidence-based design
Meta-analysis
Cost-effectiveness analysis
Stratified sampling
Non-parametric statistics