Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2009 Dec;15(6):1214-6.
doi: 10.1111/j.1365-2753.2009.01347.x.

On the causal structure of information bias and confounding bias in randomized trials

Eyal Shahar  1 , Doron J Shahar
Affiliations

On the causal structure of information bias and confounding bias in randomized trials

Eyal Shahar et al. J Eval Clin Pract. 2009 Dec.

Abstract

Randomized trials are undoubtedly different from observational studies, but authors sometimes propose differences between these designs that do not exist. In this article we examine two claims about randomized trials: first, a recent claim that the causal structure of exposure measurement (information) bias in a randomized trial differs from the causal structure of that bias in an observational study. Second, a long-standing claim that confounding bias cannot operate in a randomized trial - if randomization was perfectly implemented. Using causal diagrams (causal directed acyclic graphs), we show that both claims are false in the context of an intention-to-treat analysis. We also describe a previously unrecognized mechanism of information bias, and suggest that the term 'information bias' should replace the terms 'measurement bias' and 'observation bias'.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

LinkOut - more resources