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Review
. 2011 Nov;101(11):2164-9.
doi: 10.2105/AJPH.2011.300264. Epub 2011 Sep 22.

Studies with staggered starts: multiple baseline designs and group-randomized trials

Dale A Rhoda  1 , David M Murray, Rebecca R Andridge, Michael L Pennell, Erinn M Hade
Affiliations
Review

Studies with staggered starts: multiple baseline designs and group-randomized trials

Dale A Rhoda et al. Am J Public Health. 2011 Nov.

Erratum in

  • Am J Public Health. 2014 Mar;104(3):e12

Abstract

Objectives: Multiple baseline designs (MBDs) have been suggested as alternatives to group-randomized trials (GRT). We reviewed structural features of MBDs and considered their potential effectiveness in public health research. We also reviewed the effect of staggered starts on statistical power.

Methods: We reviewed the MBD literature to identify key structural features, recent suggestions that MBDs be adopted in public health research, and the literature on power in GRTs with staggered starts. We also computed power for MBDs and GRTs.

Results: The features that have contributed to the success of small MBDs in some fields are not likely to translate well to public health research. MBDs can be more powerful than GRTs under some conditions, but those conditions involve assumptions that require careful evaluation in practice.

Conclusions: MBDs will often serve better as a complement of rather than as an alternative to GRTs. GRTs may employ staggered starts for logistical or ethical reasons, but this will always increase their duration and will often increase their cost.

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Figures

FIGURE 1
FIGURE 1
Conceptual diagram of the multiple baseline or stepped wedge design. Note. The intervention commences on a staggered schedule across groups with the idea that a measureable effect in the outcome variable(s) will follow a similar pattern.
FIGURE 2
FIGURE 2
Conceptual comparison of (a) stepped wedge and (b) parallel group-randomized trial designs. Note. Intervention and control conditions are represented with both shading and the 0/1 Xij nomenclature of Hussey and Hughes. A 0 means the group is in the control condition, and a 1 means the group is in the intervention condition.
FIGURE 3
FIGURE 3
The variance of the estimator using a parallel group-randomized trial design from Equation 5 divided by the variance of the estimator using a stepped wedge design from Equation 4, assuming equal numbers of groups and measurement occasions, and 50 persons per group for various numbers of measurement occasions and ICCs from 0.0 to 0.5. Note. GRT = parallel group-randomized trial; ICC = intraclass correlation coefficient; SWD = stepped wedge design; T = number of measurement occasions.
See this image and copyright information in PMC

References

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