Application of flow diagram approach to Scenario 1
| 1. Research question | Is posturing advisable in patients undergoing vitrectomy surgery? |
| 2. Null hypothesis | There is no difference in risk of failure between patients undergoing vitrectomy surgery in Group A (posturing) and Group B (no posturing). |
| 3. Result | Odds in Group A=1/199 Odds in Group B=2/198 OR=2.02 95% CI=0.18 to 22.3 p=0.999 |
| 4. Interpretation | The best estimate of the OR is 2, that is, failure is twice as common in the non-posturing group as it is the posturing group. There is however a lot of uncertainty with this estimate. The trial data means that it is plausible that the odds are the same in the two groups; however it is still possible that the odds are actually more than 20 times in the non-posturing group or as little as a fifth as high. If we were to simply consider the p value none of this uncertainty would be apparent and we would be far more tempted to simply say that there is no evidence of a difference in failure rates. |