Table 4. MNAR example: Results from a hypothetical clinical trial evaluating the effect of treatment on improvement in body fat.
| a. Results from the whole study population. | ||||
|
Outcome
|
||||
| Treatment | Y | N | ||
| • Risk Ratio=(315/600)/(210/600)=1.5 | ||||
| A | 315 | 285 | 600 | • 95% CI =1.31, 1.71 |
| B | 210 | 390 | 600 | • Chi-Square=37.3 P<0.001 |
| 525 | 675 | 1200 | ||
|
| ||||
| b. Results from completers following missing data from a Missing Not At Random Mechanism*. | ||||
|
| ||||
|
Outcome
|
||||
| Treatment | Y | N | ||
| • Risk Ratio=(189/474)/(210/444)=0.84 | ||||
| A | 189 | 285 | 474 | • 95% CI =0.73, 0.98 |
| B | 210 | 234 | 444 | • Chi-Square=5.14 P=0.02 |
| 399 | 519 | 918 | ||
*Probabilities of missing are dependent on the treatment and outcome to mimic an MNAR mechanism
Probability Missing for Outcome “Y” in Trt A = 0.40
Probability Missing for Outcome “N” in Trt A = 0.00
Probability Missing for Outcome “Y” in Trt B = 0.00
Probability Missing for Outcome “N” in Trt B = 0.40