Users' Guides to the Medical Literature
Guyatt G, Rennie D, Meade MO, Cook DJ
Part B Therapy
Chapter 10.3. What Determines the Width of the Confidence Interval?
Jan Brożek
Sample Size Does Not Determine the Width of the Confidence Interval
Topics Discussed:
confidence interval, precision of effects, sample size, study design
Excerpt:
"Clinicians sometimes equate the size of a randomized
trial or the number of participants in a trial
of therapy with its precision, and thus the width of the confidence interval (CI).
This chapter deals with issues of precision and the resulting confidence
in estimates of treatment effects in studies in which the outcomes are dichotomous (yes/no)
events such as death, stroke, or myocardial infarction. As it turns
out, the number of patients is a secondary determinant of our confidence
in estimates of reduction in adverse outcomes associated with an experimental intervention...."
Log in to read the full chapter:
Get full access to JAMAevidence two ways:
Subscribe to JAMAevidence
JAMAevidence is a subscription-
based website dedicated to the learning, teaching, and practicing of evidence-based medicine.
Pay Per View
Timed access to all of JAMAevidence
24 hours for $29.95
48 hours for $49.95