Document Detail

Comparison of intraclass correlation coefficient estimates and standard errors between using cross-sectional and repeated measurement data: the Safety Check cluster randomized trial.
MedLine Citation:
PMID:  21070889     Owner:  NLM     Status:  MEDLINE    
Designing cluster randomized trials in clinical studies often requires accurate estimates of intraclass correlation, which quantifies the strength of correlation between units, such as participants, within a cluster, such as a practice. Published ICC estimates, even when available, often suffer from the problem of wide confidence intervals. Using data from a national, randomized, controlled study concerning violence prevention for children--the Safety Check--we compare the ICC values derived from two approaches only baseline data and using both baseline and follow-up data. Using a variance component decomposition approach, the latter method allows flexibility in handling complex data sets. For example, it allows for shifts in the outcome variable over time and for an unbalanced cluster design. Furthermore, we evaluate the large-sample formula for ICC estimates and standard errors using the bootstrap method. Our findings suggest that ICC estimates range from 0.012 to 0.11 for providers within practice and range from 0.018 to 0.11 for families within provider. The estimates derived from the baseline-only and repeated-measurements approaches agree quite well except in cases in which variation over repeated measurements is large. The reductions in the widths of ICC confidence limits from using repeated measurement over baseline only are, respectively, 62% and 42% at the practice and provider levels. The contribution of this paper therefore includes two elements, which are a methodology for improving the accuracy of ICC, and the reporting of such quantities for pediatric and other researchers who are interested in designing clustered randomized trials similar to the current study.
Edward H Ip; Richard Wasserman; Shari Barkin
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.     Date:  2010-11-08
Journal Detail:
Title:  Contemporary clinical trials     Volume:  32     ISSN:  1559-2030     ISO Abbreviation:  Contemp Clin Trials     Publication Date:  2011 Mar 
Date Detail:
Created Date:  2011-02-07     Completed Date:  2011-06-01     Revised Date:  2014-09-24    
Medline Journal Info:
Nlm Unique ID:  101242342     Medline TA:  Contemp Clin Trials     Country:  United States    
Other Details:
Languages:  eng     Pagination:  225-32     Citation Subset:  IM    
Copyright Information:
Copyright © 2010 Elsevier Inc. All rights reserved.
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MeSH Terms
Bias (Epidemiology)
Child, Preschool
Cluster Analysis
Confidence Intervals
Cross-Sectional Studies / methods*
Data Interpretation, Statistical
Mass Media
Outcome Assessment (Health Care) / standards,  statistics & numerical data
Pediatrics / methods
Randomized Controlled Trials as Topic / methods*,  statistics & numerical data
Statistics as Topic / methods*
Violence / prevention & control,  psychology,  statistics & numerical data
Grant Support
R01 AG031827/AG/NIA NIH HHS; R01 AG031827-01A2/AG/NIA NIH HHS; R01 HD 42260/HD/NICHD NIH HHS; RBOMC00107//PHS HHS; U01 HL101066/HL/NHLBI NIH HHS; U01 HL101066-01/HL/NHLBI NIH HHS

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