FAQ/OddsRa - CBU statistics Wiki

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Odds Ratios are useful in summarising the effect size or magnitude of a difference in a 2x 2 table.

For example

Group

Sober

Drunk

Complied

106

9

Refused

59

56

Odds Ratio = (106/9) / (59/56) = (106x56) / (9x59) = 11.18

The compliers were 11 times more likely to be sober than the refusers.

You can obtain a confidence interval for the odds ratio using some simple calculations or by clicking on risk under statistics in the crosstabs procedure in SPSS.