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. 2015 May 7;34(21):2899–2912. doi: 10.1002/sim.6523

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Copyright © 2015 © 2015 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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Empirical differences in sampling fractions between the asymptotically-optimal design and the two-stage adaptive designs employing proportional stratified sampling in phase-IIa according to the percentage of the phase-II sample that is selected at phase-IIb (n^(b)/n) for a binary expensive covariate; N = 800; n = 200; (β₀,β_x,β_v) = (−1.95,1.00,0.90), (α₀,α_v) = (1.05,−0.41), and γ₀=−0.04 ; n_YV represents the number of individuals selected for the measurement of X from the available N_YV individuals in stratum (Y,V) in the two-stage adaptive design, while represents the corresponding sample size for the asymptotically-optimal design. This two-stage adaptive design was derived for selecting individuals for measurement of a binary X and relied on either parametric or empirical estimation of design components from data collected in phase-I and phase-IIa.

Inline graphic — Empirical differences in sampling fractions between the asymptotically-optimal design and the two-stage adaptive designs employing proportional stratified sampling in phase-IIa according to the percentage of the phase-II sample that is selected at phase-IIb (n^(b)/n) for a binary expensive covariate; N = 800; n = 200; (β₀,β_x,β_v) = (−1.95,1.00,0.90), (α₀,α_v) = (1.05,−0.41), and γ₀=−0.04 ; n_YV represents the number of individuals selected for the measurement of X from the available N_YV individuals in stratum (Y,V) in the two-stage adaptive design, while represents the corresponding sample size for the asymptotically-optimal design. This two-stage adaptive design was derived for selecting individuals for measurement of a binary X and relied on either parametric or empirical estimation of design components from data collected in phase-I and phase-IIa.