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Exercise: Prophylactic administration of parenteral steroids, answer 4

Question 4: What kind of horizontal scale is used in Figure 1 and why?

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Suggested answer:

This is a logarithmic scale, where equal intervals represent equal ratios
rather than equal differences.

It is used because the outcome is a ratio and an odds ratio of 0.1 is as different from 1,
representing no difference between treatments, as is an odds ratio of 10.
This makes the confidence intervals symmetrical,
because they are calculated for the log of the odds ratio
rather than for the odds ratio itself,
then antilogged to the natural scale.

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Last updated: 18 February, 2009.

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