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Type: Journal article
Title: Accounting for twin births in sample size calculations for randomised trials
Author: Yelland, L.
Sullivan, T.
Collins, C.
Price, D.
Mcphee, A.
Lee, K.
Citation: Paediatric and Perinatal Epidemiology, 2018; 32(4):380-387
Publisher: Wiley
Issue Date: 2018
ISSN: 0269-5022
Statement of
Lisa N. Yelland, Thomas R. Sullivan, Carmel T. Collins, David J. Price, Andrew J. McPhee, Katherine J. Lee
Abstract: Including twins in randomised trials leads to non-independence or clustering in the data. Clustering has important implications for sample size calculations, yet few trials take this into account. Estimates of the intracluster correlation coefficient (ICC), or the correlation between outcomes of twins, are needed to assist with sample size planning. Our aims were to provide ICC estimates for infant outcomes, describe the information that must be specified in order to account for clustering due to twins in sample size calculations, and develop a simple tool for performing sample size calculations for trials including twins.ICCs were estimated for infant outcomes collected in four randomised trials that included twins. The information required to account for clustering due to twins in sample size calculations is described. A tool that calculates the sample size based on this information was developed in Microsoft Excel and in R as a Shiny web app.ICC estimates ranged between -0.12, indicating a weak negative relationship, and 0.98, indicating a strong positive relationship between outcomes of twins. Example calculations illustrate how the ICC estimates and sample size calculator can be used to determine the target sample size for trials including twins.Clustering among outcomes measured on twins should be taken into account in sample size calculations to obtain the desired power. Our ICC estimates and sample size calculator will be useful for designing future trials that include twins. Publication of additional ICCs is needed to further assist with sample size planning for future trials.
Keywords: generalised estimating equations; intracluster correlation; multiple birth; power; statistical methodology
Rights: © 2018 John Wiley & Sons Ltd.
RMID: 0030086813
DOI: 10.1111/ppe.12471
Grant ID:
Appears in Collections:Paediatrics publications

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