The Objectives of a Randomised Controlled Trial
A trial may be conceived to test more than one hypothesis but it is good practice and usually essential when calculating the numbers required for a trial to determine one major objective. For example, an investigator may be interested in a trial of a new antihypertensive drug in elderly patients. The major objective could be either to demonstrate the efficacy of the drug in lowering blood pressure or in preventing cardiovascular deaths. The first objective could be answered in a few patients studied for six months, but the second objective would require the study of hundreds of patients over many years (chapter 10). In order to calculate the numbers required for a trial, the major objective has to be identified and the smallest effect of treatment to be detected must be defined.
KeywordsSystolic Blood Pressure Total Mortality Major Objective Stroke Mortality Antianxiety Drug
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