Table 3.
GALA results: missing mean
| Method for missing mean replacement | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Complete data result | Hozo [6] | Bland [21] | Wan [22] | None, omit study | ||||||
| Mean difference (days) | 95% confidence interval | Bias | Imprecision | Bias | Imprecision | Bias | Imprecision | Bias | Imprecision | |
| Scenario | ||||||||||
| 5 trials | −0.01 | (−0.87, 0.85) | ||||||||
| 2 missing means | −0.20 | 1.00 | −0.12 | 1.00 | 0.05 | 1.00 | 0.27 | 1.28 | ||
| 10 trials | −0.01 | (− 0.37, 0.35) | ||||||||
| 2 missing means | 0.64 | 3.47 | 0.15 | 2.15 | −0.03 | 1.00 | 0.02 | 1.06 | ||
| 5 missing means | 0.12 | 4.35 | −0.06 | 1.58 | 0.04 | 1.00 | 0.00 | 1.64 | ||
| 20 trials | 0.00 | (−0.31, 0.30) | ||||||||
| 5 missing means | 1.16 | 3.67 | 0.38 | 2.30 | −0.03 | 1.00 | 0.02 | 1.25 | ||
| 10 missing means | 1.02 | 4.34 | 0.34 | 2.66 | 0.01 | 1.00 | 0.05 | 1.41 | ||
| 30 trials | −0.01 | (−0.28, 0.25) | ||||||||
| 5 missing means | 0.02 | 1.43 | 0.01 | 1.15 | 0.01 | 1.00 | 0.09 | 1.15 | ||
| 10 missing means | 0.01 | 2.92 | 0.06 | 1.89 | 0.04 | 1.00 | −0.02 | 1.62 | ||
| 15 missing means | −0.19 | 3.26 | −0.05 | 2.13 | 0.03 | 1.00 | 0.12 | 2.19 | ||
Results are given for mixed sample size scenario (average of 60 patients per trial) and random allocation of trials to missing mean values. Imprecision is the ratio of widths of confidence intervals for the intervention effect [width when estimating missing means: width when all means available] Results for other scenarios (small trials, large trials; missing mean in small trials, large trials) show similar patterns (online Additional file 3 Tables S9-S16)