Evaluating the Internal Validity of a Randomized Controlled Trial

s this treatment effective? The best study to answer this question is a randomized controlled trial (RCT). Once a RCT is found to answer the therapeutic question of interest the reader must decide whether or not the authors took all of the important steps to minimize bias. The strength of the inference that we can take from the trial is based upon how well the authors have planned, executed and reported safeguards to minimize bias in their study. The authors could reach an invalid conclusion to the question either because of bias or random error. The evaluation of the safeguards implemented by the authors is referred to as the internal validity of a RCT. Methodological quality is a continuum not a dichotomy and is often in the eye of the beholder.