RT Book, Section A1 Guyatt, Gordon A1 Jaeschke, Roman A1 Meade, Maureen O. A2 Guyatt, Gordon A2 Rennie, Drummond A2 Meade, Maureen O. A2 Cook, Deborah J. SR Print(0) ID 1183875674 T1 Why Study Results Mislead: Bias and Random Error T2 Users' Guides to the Medical Literature: A Manual for Evidence-Based Clinical Practice, 3rd ed YR 2015 FD 2015 PB McGraw-Hill Education PP New York, NY SN 978-0-07-179071-0 LK jamaevidence.mhmedical.com/content.aspx?aid=1183875674 RD 2024/10/15 AB Our clinical questions have correct answers that correspond to an underlying reality or truth. For instance, there is a true underlying magnitude of the impact of β-blockers on mortality in patients with heart failure, the impact of inhaled corticosteroids on exacerbations in patients with asthma, the impact of reamed vs unreamed nailing of tibial fractures, the prognosis of patients with hip osteoarthritis, and the diagnostic properties of a pregnancy test. Research studies attempt to estimate that underlying truth. Unfortunately, however, we will never know the exact truth. Studies may be flawed in their design or conduct and introduce systematic error (or bias). Even if a study could be perfectly designed and executed, the estimated treatment effect may miss the mark because of random error. The next section explains why.