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Blinded versus unblinded estimation of a correlation coefficient to inform interim design adaptations

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Kunz, Cornelia, Stallard, Nigel, Parsons, Nicholas R., Todd, Susan and Friede, Tim (2017) Blinded versus unblinded estimation of a correlation coefficient to inform interim design adaptations. Biometrical Journal, 59 (2). pp. 344-357. doi:10.1002/bimj.201500233

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Official URL: http://doi.org/10.1002/bimj.201500233

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Abstract

Regulatory authorities require that the sample size of a confirmatory trial is calculated prior to the start of the trial. However, the sample size quite often depends on parameters which might not be known in advance of the study. Misspecification of these parameters can lead to under- or overestimation of the sample size. Both situations are unfavourable as the first one decreases the power and the latter one leads to a waste of resources. Hence, designs have been suggested that allow a re-assessment of the sample size in an ongoing trial. These methods usually focus on estimating the variance. However, for some methods the performance depends not only on the variance but also on the correlation between measurements. We develop and compare different methods for blinded estimation of the correlation coefficient which are less likely to introduce operational bias when the blinding is maintained. Their performance with respect to bias and standard error is compared to the unblinded estimator. We simulated two different settings: one assuming that all group means are the same and one assuming that different groups have different means. Simulation results show that the naïve (onesample) estimator is only slightly biased and has a standard error comparable to that of the unblinded estimator. However, if the group means differ, other estimators have better performance depending on the sample size per group and the number of groups.

Item Type: Journal Article
Subjects: R Medicine > R Medicine (General)
Divisions: Faculty of Medicine > Warwick Medical School > Health Sciences
Faculty of Medicine > Warwick Medical School > Health Sciences > Statistics and Epidemiology
Faculty of Medicine > Warwick Medical School
Library of Congress Subject Headings (LCSH): Clinical trials -- Statistical methods -- Research
Journal or Publication Title: Biometrical Journal
Publisher: Wiley - V C H Verlag GmbH & Co. KGaA
ISSN: 0323-3847
Official Date: March 2017
Dates:
DateEvent
March 2017Published
25 November 2016Available
14 June 2016Accepted
Volume: 59
Number: 2
Page Range: pp. 344-357
DOI: 10.1002/bimj.201500233
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Open Access
Funder: Medical Research Council (Great Britain) (MRC), Seventh Framework Programme (European Commission) (FP7)
Grant number: Grant number G1001344 (MRC), FP HEALTH 2013 -- 602144 (FP7)
RIOXX Funder/Project Grant:
Project/Grant IDRIOXX Funder NameFunder ID
G1001344[MRC] Medical Research Councilhttp://dx.doi.org/10.13039/501100000265
602144FP7 Healthhttp://dx.doi.org/10.13039/100011272
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