These tools will help you to interpret the clinical and statistical significance of data reported in clinical research.
Diagnostic Test Calculator
Clinical Calculator I
Clinical Calculator II
How to Read a Paper: The Basics of Evidence-based Medicine is available as an E-book from ECPI Library. Read it online:
Three criteria to keep in mind:
Quality
Trials that are randomised and double blind, to avoid selection and observer bias, and where we know what happened to most of the subjects in the trial.
Validity
Trials that mimic clinical practice, or could be used in clinical practice, and with outcomes that make sense. For instance, in chronic disorders we want long-term, not short-term trials. We are [also] ... interested in outcomes that are large, useful, and statistically very significant (p < 0.01, a 1 in 100 chance of being wrong).
Size
Trials (or collections of trials) that have large numbers of patients, to avoid being wrong because of the random play of chance. For instance, to be sure that a number needed to treat (NNT) of 2.5 is really between 2 and 3, we need results from about 500 patients. If that NNT is above 5, we need data from thousands of patients.
These are the criteria on which we should judge evidence. For it to be strong evidence, it has to fulfil the requirements of all three criteria."
Evidence-Based Nursing: an Evidence-Based Nursing Tutorial from the Information Services Department of the Library of the Health Sciences-Chicago, University of Illinois at Chicago.