Absence of evidence is not evidence of absence

BMJ 1995;311:485 (19 August) – Statistics notes – Absence of evidence is not evidence of absence

Douglas G Altman,  J Martin Bland

“Randomised controlled clinical trials that do not show a significant difference between the treatments being compared are often called “negative.” This term wrongly implies that the study has shown that there is no difference, whereas usually all that has been shown is an absence of evidence of a difference. These are quite different statements.”

“While it is usually reasonable not to accept a new treatment unless there is positive evidence in its favour, when issues of public health are concerned we must question whether the absence of evidence is a valid enough justification for inaction.”

“When we are told that “there is no evidence that A causes B” we should first ask whether absence of evidence means simply that there is no information at all”

Filed under: Evidence Based Practice, MT research issues, Research education, evidence, p-value, RCT

University of Manitoba sanctions researcher over phoney science

This case highlights the necessity of confirming study result with replication of the initial work.

Research can be faked,  how ever more commonly researchers can make a mistake in the study design or their reporting of the results. When clinicians search for research to inform their practises it is crucial for them to be aware of the strength and quality of the research they are intending to use.

Filed under: Evidence Based Practice, MT research issues, Research news, phoney science, research

All Canadians now have one-click access to The Cochrane Library!

Canadians now have online access to the world’s largest library of systematic reviews of health care treatments.

The Cochrane Library is now available on the web at www.thecochranelibrary.com, opening up a renowned international vault of reputable reviews of medical studies.

Cochrane studies are peer-reviewed and not funded by third parties, such as pharmaceutical companies. They offer abstracts for health care professionals and 300-word summaries in plain English.

Filed under: Announcements, Evidence Based Practice, Library, Research databases, Resources

Why Most Published Research Findings Are False

Ioannidis JPA

Summary

There is increasing concern that most current published research findings are false. The probability that a research claim is true may depend on study power and bias, the number of other studies on the same question, and, importantly, the ratio of true to no relationships among the relationships probed in each scientific field. In this framework, a research finding is less likely to be true when the studies conducted in a field are smaller; when effect sizes are smaller; when there is a greater number and lesser preselection of tested relationships; where there is greater flexibility in designs, definitions, outcomes, and analytical modes; when there is greater financial and other interest and prejudice; and when more teams are involved in a scientific field in chase of statistical significance. Simulations show that for most study designs and settings, it is more likely for a research claim to be false than true. Moreover, for many current scientific fields, claimed research findings may often be simply accurate measures of the prevailing bias. In this essay, I discuss the implications of these problems for the conduct and interpretation of research.

PLoS Medicine 2(8): e124. – full text

doi:10.1371/journal.pmed.0020124

Filed under: Evidence Based Practice, MT research issues, Research education

CEBM keeps on improving

CEBM as one of the best evidence based practice website out-there keeps on getting better. They have recently made significant improvement to their website.

Take a look here http://www.cebm.net/

Filed under: Evidence Based Practice, Knowledge translation, Tutorials