Question 4: When cough is the row variable and history of bronchitis the column variable, how can we interpret the Risk Estimate table?
This is the Risk Estimate table output by SPSS:
| Risk Estimate | |||
|---|---|---|---|
| Value | 95% Confidence Interval | ||
| Lower | Upper | ||
| Odds Ratio for Day or night cough at age 12 (Yes / No) | 2.397 | 1.448 | 3.970 |
| For cohort Bronchitis by age 5 = Yes | 1.878 | 1.358 | 2.598 |
| For cohort Bronchitis by age 5 = No | .784 | .653 | .940 |
| N of Valid Cases | 1319 | ||
We have odd ratio = 2.40 with 95% confidence interval = 1.45 to 3.97, as before.
The second row of the table gives the relative risk of having a history of bronchitis for those children reported to cough, compared to the risk of having a history of bronchitis for those children not reported to cough. It was found by (26/70) / (247/1249) = 1.878.
The third row of the table gives the relative risk of not having a history of bronchitis for those children reported to cough, compared to the risk of not having a history of bronchitis for those children not reported to cough. It was found by (44/70) / (1002/1249) = 0.784.
Neither of these relative risks is much use.
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Last updated: 21 November, 2006.