Question 2: Calculate the odds ratio and relative risk for the relationship. Quote the results to two decimal places.
As before, we choose Analyze, Descriptive Statistics, Crosstabs. Put the variable 'Bronchitis by age 5' into Row(s): and 'Day or night cough at age 12' into Column(s):. Click Statistics, Chisquare. This time we click Risk, Continue. Click OK.
You should get the case processing summary, cross-tabulation, and chi-squared test as before. You should then see the following:
| Risk Estimate | |||
|---|---|---|---|
| Value | 95% Confidence Interval | ||
| Lower | Upper | ||
| Odds Ratio for Bronchitis by age 5 (Yes / No) | 2.397 | 1.448 | 3.970 |
| For cohort Day or night cough at age 12 = Yes | 2.264 | 1.420 | 3.609 |
| For cohort Day or night cough at age 12 = No | .944 | .907 | .984 |
| N of Valid Cases | 1319 | ||
We have odd ratio = 2.40 with 95% confidence interval = 1.45 to 3.97.
The second row of the table gives the relative risk of cough for bronchitis = 2.26, 95% confidence interval = 1.42 to 3.61.
The third row of the table gives the relative risk of not coughing for bronchitis. It is the risk of no cough for those with a history of bronchitis divided by the risk of no cough for those without a history of bronchitis, (247/273) / (1002/1046) = 0.94.
Back to Exercise: Cough during the day or at night and history of bronchitis.
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Last updated: 21 November, 2006.