Estimation and Standardization of Variance Parameters for Planning Cluster-Randomized Trials: A Short Guide for Researchers

Year 2019, Volume: 10 Issue: 2, 179 - 201, 28.06.2019

Metin Buluş , Sakine Göçer Şahin

https://doi.org/10.21031/epod.530642

Cited By: 5

Abstract

A review of
literature covering the past decade indicates a shortage of cluster-randomized
trials (CRTs) in education and psychology in Turkey, the gold standard that is
capable of producing high-quality evidence for high-stake decision making when
individual randomization is not feasible. Scarcity of CRTs is not only
detrimental to collective knowledge on the effectiveness of interventions but
also hinders efficient design of such studies as prior information is at best
incomplete or unavailable. In this illustration, we demonstrate how to estimate
variance parameters from existing data and transform them into standardized
forms so that they can be used in planning sufficiently powered CRTs. The
illustration uses publicly available software and guides researchers step by
step via introducing statistical models, defining parameters, relating them to
notations in statistical models and power formulas, and estimating variance
parameters. Finally, we provide example statistical power and minimum required
sample size calculations.  

Keywords

cluster-randomized trials, variance estimation, statistical power analysis, minimum required sample size

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