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Tips for Teachers of Evidence-Based Medicine: Understanding Odds Ratios and Their Relationship to Risk Ratios

By Kameshwar Prasad, Roman Jaeschke, Peter Wyer, Sheri Keitz and Gordon Guyatt
Topics: Teaching Tips
Publisher: Springer-Verlag
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Provided by: PubMed Central

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  3. As you approach the lower risk values, lead the learners to the realization that the decimal values for risk and odds converge and are virtually identical at the point the risk is
  4. Ask the learners to calculate the ratio of odds for the outcome between the groups (0.67/1.0=0.67)
  5. Ask the learners to calculate the ratio of risk for the outcome between the groups (0.4/0.5=0.80).
  6. (1994). Clinically useful measures of effect in binary analyses of randomized trials.
  7. Construct a figure on a blackboard or flip chart with risk expressed as a decimal (e.g., 0.25), odds expressed as a ratio (e.g., 1:3), odds expressed as a decimal (e.g., 0.33) and odds illustrated using markers (e.g., X/XXX) in successive columns.
  8. (1996). Down with odds ratios!. Evidence Based Med.
  9. Fill in the fourth column with the symbols you have selected to further illustrate the process.
  10. Fill in the table with 40 of 100 treated patients and 50 of 100 control patients in the outcome positive column.
  11. Lead the learners to understand that the relative odds are further from 1 than the relative risk, implying a greater relative reduction in frequency of the outcome.
  12. (1990). Some statistical methods for combining experimental results.
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