Question 1: What is meant by "odds ratio 0.80" and how was it calculated?
The odds of death or be admission to an intensive care unit is the number who die or are admitted divided by the number who do not die and are not admitted to intensive care, i.e. the number with a bad outcome divided by the number with a good outcome.
For patients on statins, the odds of a bad outcome = 50/(325 – 50).
For patients not on statins, the odds of a bad outcome = 574/(3090 – 574)
Odds ratio = the odds of a bad outcome among patients on statins divided by the odds of a bad outcome among patients not on statins, (50/(325 – 50)) / (574/(3090 – 574)) = 0.80.
Hence, in this sample patients on statins were less likely to have a bad outcome than patients who were not on statins.
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Last updated: 2 March, 2009.