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. 2013 Dec 13;15(2):251–265. doi: 10.1093/biostatistics/kxt055

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© The Author 2013. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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Figure 1. — (A) Displays the curve which is constant over all time-points t and the curve for several time points for a useless surrogate in the time-independent hazard Weibull setting. (B) Displays the curve for a high-quality surrogate in the time-independent hazard setting and several curves for different time points t for this same surrogate scenario. (C) Displays curves for given amounts of follow-up time after and over the range of for a high-quality surrogate. These curves illustrate time variation in TE that is both associated with the candidate surrogate and exists when ; the figure depicts a candidate surrogate that declines in value over time while the average TE is remaining approximately the same over time. (D) Displays curves for given levels of over a range of follow-up times () in years for a medium-quality surrogate. These curves illustrate time variation in TE that is approximately equal over all levels of the candidate surrogate; the figure depicts a candidate surrogate that retains some value as a PS over time but for declining TE.

Inline graphic — (A) Displays the curve which is constant over all time-points t and the curve for several time points for a useless surrogate in the time-independent hazard Weibull setting. (B) Displays the curve for a high-quality surrogate in the time-independent hazard setting and several curves for different time points t for this same surrogate scenario. (C) Displays curves for given amounts of follow-up time after and over the range of for a high-quality surrogate. These curves illustrate time variation in TE that is both associated with the candidate surrogate and exists when ; the figure depicts a candidate surrogate that declines in value over time while the average TE is remaining approximately the same over time. (D) Displays curves for given levels of over a range of follow-up times () in years for a medium-quality surrogate. These curves illustrate time variation in TE that is approximately equal over all levels of the candidate surrogate; the figure depicts a candidate surrogate that retains some value as a PS over time but for declining TE.