Abstract

Abstract When investigating the effects of potential prognostic or risk factors that have been measured on a quantitative scale, values of these factors are often categorized into two groups. Sometimes an ‘optimal’ cutpoint is chosen that gives the best separation in terms of a two‐sample test statistic. It is well known that this approach leads to a serious inflation of the type I error and to an overestimation of the effect of the prognostic or risk factor in absolute terms. In this paper, we illustrate that the resulting confidence intervals are similarly affected. We show that the application of a shrinkage procedure to correct for bias, together with bootstrap resampling for estimating the variance, yields confidence intervals for the effect of a potential prognostic or risk factor with the desired coverage. Copyright © 2004 John Wiley & Sons, Ltd.

Keywords

Confidence intervalStatisticsResamplingStatisticSelection (genetic algorithm)Variance (accounting)Test statisticInflation (cosmology)MathematicsComputer scienceStatistical hypothesis testing

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Publication Info

Year
2004
Type
article
Volume
23
Issue
11
Pages
1701-1713
Citations
116
Access
Closed

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Norbert Holländer, Willi Sauerbrei, Martin Schumacher (2004). Confidence intervals for the effect of a prognostic factor after selection of an ‘optimal’ cutpoint. Statistics in Medicine , 23 (11) , 1701-1713. https://doi.org/10.1002/sim.1611

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DOI
10.1002/sim.1611