Evaluation & the Health Professions

 

Advanced Search

Journal Navigation

Journal Home

Subscriptions

Archive

Contact Us

Table of Contents

Click here to register today!

Click here to register today!

Sign In to gain access to subscriptions and/or personal tools.
This Article
Right arrow Full Text (PDF)
Right arrow References
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to Saved Citations
Right arrow Download to citation manager
Right arrowReprints and Permissions
Right arrow Add to My Marked Citations
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Weeks, D. L.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Weeks, D. L.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati  
What's this?
Evaluation & the Health Professions, Vol. 30, No. 3, 254-265 (2007)
DOI: 10.1177/0163278707304043
© 2007 SAGE Publications

Reviews

The Regression Effect as a Neglected Source of Bias in Nonrandomized Intervention Trials and Systematic Reviews of Observational Studies

Douglas L. Weeks

Inland Northwest Health Services Washington State University-Spokane

Health care providers depend on the findings of observational intervention studies and systematic reviews of those studies to make evidence-based decisions about their clients' care. The nonrandom methods of group formation in observational studies necessitate carefully assessing threats to the validity of conclusions. Regression to the mean is a source of change in clinical outcome measures that has escaped widespread notice as a potential threat to the accuracy of conclusions from observational studies and systematic reviews thereof. Failure to assess the degree to which regression confounds study results elevates the risk of making clinical decisions using biased estimates of intervention effectiveness. Because the change in average outcome scores due to regression can be quantified, it is a type of bias whose direct influence can be known. Yet determining and reporting change due to regression is uncommon in observational studies or systematic reviews thereof. The means to quantify change due to regression in average outcome scores is illustrated by example in this article.

Key Words: evidence-based practice • meta-analysis • statistical regression • systematic review • cohort study • case-control study • internal validity


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati    What's this?