Table 1.
(a) Evidence scenario and description |
(b) Precision (variance) input by level of evidence |
(c)obtained for an IC using values in (b) |
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Scenario | Description | Direct A vs. B (Fig. 1A) | All first-order indirect (Fig. 1D) | All second-order indirect (Fig. 1F) | Direct evidence | First-order IC | Second-order IC |
1 | Evidence available in equal amounts for all comparisons | P = 1 (V = 1) | P = 1 (V = 1) | P = 1 (V = 1) | 1 | 2 | 3 |
2 | Sparse network; a few small trials/weak evidence available for direct and first order. Stronger evidence for second order | P = 0.5 (V = 2) | P = 0.75 (V = 1.33) | P = 1 (V = 1) | 2 | 2.66 | 3.66 |
3 | Few trials/weak direct evidence on focal treatments. More evidence for first- and second-order comparisons | P = 0.5 (V = 2) | P = 2 (V = 0.5) | P = 5 (V = 0.2) | 2 | 1 | 1.2 |
4 | Strong direct evidence available for focal treatments. All other evidence weaker | P = 5 (V = 0.2) | P = 2 (V = 0.5) | P = 1 (V = 1) | 0.2 | 1 | 2 |
5 | Well-populated network; several trials. Strong evidence available for each comparison | P = 5 (V = 0.2) | P = 3 (V = 0.33) | P = 3 (V = 0.33) | 0.2 | 0.66 | 0.99 |
Notes. Evidence scenarios and corresponding precision input values for each level of evidence in the six-treatment network. “All first-order indirect” refers to evidence on a treatment contrast that contributes to a first-order IC, i.e., A vs. C, …, B vs. F. The variance for a first-order IC is formed, e.g., “All second-order indirect” refers to evidence on a treatment contrast that contributes to a second-order IC, i.e., C vs. D, …, E vs. F. The variance for a second-order IC is formed, e.g., .
IC, indirect comparison; P, precision; V, variance.