Odds Ratios are useful in summarising the effect size or magnitude of a difference in a 2x 2 table.
For example
- 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 thso dds ratio [FAQ:oddsr:using some simple calculations] or by clicking on risk under statistics in the crosstabs procedure in SPSS.