Question 1: The program used for the analysis in Week 7 (Stata 8) gives the following statistics:
Risk difference = 0.196 (95% CI -0.091 to 0.483)
Risk ratio = 2.88 (95% CI 1.02 to 8.10)
Odds ratio = 3.69 (95% CI 0.96 to 14.32)
What do each of these statistics mean?
Risk difference = the difference between the proportion of diabetics who report high blood pressure and the proportion of non-diabetics who report high blood pressure, 3/10 - 20/192 = 0.3000 - 0.1042 = 0.196.
Risk ratio = the proportion of diabetics who report high blood pressure divided by the proportion of non-diabetics who report high blood pressure, (3/10) / (20/192) = 0.3000 / 0.1042 = 2.88.
The odds of high blood pressure is the number with high blood pressure divided by the number without high blood pressure.
Odds ratio = the odds of reporting high blood pressure among diabetics divided by the odds of reporting high blood pressure among non-diabetics, (3/7) / (20/172) = 0.4286 / 0.1163 = 3.69.
Back to Exercise: Diabetes and high blood pressure in the 2005 M.Sc. questionnaire, Part 2.
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Last updated: 20 November, 2006.