Imputation method | Mean Absolute Error (kg) | |||
---|---|---|---|---|
Study I weight extrapolation N=1472 | Study II weight interpolation N=2131 | |||
Mixed-effects models | All weights included (n=6272) | Dropping third trimester weights (n=3375) | All weights included (n=11,775) | Dropping third trimester weights (n=8125) |
 3 knots (quartiles) | 1.99 | 2.01 | 1.69 | 1.64 |
 4 knots (quintiles) | 2.08 | 2.05 | 1.66 | 1.59 |
 5 knots (sextiles) | 2.18 | N/Aa | 1.60 | 1.70 |
 3 knots (5th, 50th, 95th) | 2.00 | 2.00 | 1.67 | 1.63 |
 4 knots (5th, 35th, 65th, 95th) | 2.00 | 1.98 | 1.62 | 1.66 |
 5 knots (5th, 27.5th, 50th, 72.5th, 95th) | 2.25 | 1.98 | 1.60 | 1.81 |
 Linear | 2.02 | 2.01 | 1.67 | 1.65 |
 Quadratic | 2.02 | 1.95 | 1.66 | 1.62 |
 Cubic | 2.02 | 6.46 | 1.62 | N/Aa |
Marginal models with GEE | Mean residual | Nearest weight residual | Mean residual | Nearest weight residual |
 3 knots (quartiles) | 2.94 | 3.94 | 2.03 | 1.98 |
 4 knots (quintiles) | 2.94 | 3.94 | 2.00 | 1.97 |
 5 knots (sextiles) | 2.94 | 3.94 | 1.96 | 1.96 |
 3 knots (5th, 50th, 95th) | 2.94 | 3.94 | 2.02 | 1.97 |
 4 knots (5th, 35th, 65th, 95th) | 2.94 | 3.93 | 1.97 | 1.96 |
 5 knots (5th, 27.5th, 50th, 72.5th, 95th) | 2.94 | 3.92 | 1.95 | 2.01 |
 Linear | 2.94 | 3.94 | 2.01 | 2.03 |
 Quadratic | 2.94 | 3.94 | 2.02 | 1.98 |
 Cubic | 2.93 | 3.92 | 1.97 | 1.96 |
Assigning the nearest weight measure | 2.46 | 2.14 | ||
Arithmetic imputation using the nearest two weight measures | 2.91 | 2.00 |