A Randomized Controlled Trial Is Conducted to Evaluate the Safety

question 34

Multiple Choice

A randomized controlled trial is conducted to evaluate the safety and efficacy of monotherapy with a new disease-modifying antirheumatic drug (DMARD) after switching from methotrexate versus continuing methotrexate in patients with inadequate response to methotrexate.  The study enrolled adults (age ≥18) who fulfilled the American College of Rheumatology (ACR) -European League Against Rheumatism (EULAR) classification criteria for rheumatoid arthritis.  The investigators defined monotherapy with the new DMARD as effective if the treatment resulted in a 20% improvement in the ACR criteria (ACR20) at week 14.  In designing the study, the researchers set the probability of wrongly finding that DMARD monotherapy after switching from methotrexate is more effective than continuing methotrexate as 1%, and they set the probability of wrongly finding that the effectiveness of the two therapies is the same as 5%.  Which of the following is the most accurate estimate of the statistical power in this study?

• A)1%
• B)5%
• C)20%
• D)95%
• E)99%

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