Table 2.
Select summary of sample size methods for stepped wedge cluster randomized trials and related software.
| Outcome Type | Design | Analysis | Software | Reference |
|---|---|---|---|---|
| Continuous | Cross-sectional | Linear mixed model (random intercept) |
swCRTdesign (R)
74
swdpwr (R) 61 SWSamp (R) 75 SteppedPower (R) * %swdpwr (SAS macro) 61 steppedwedge (Stata) 76 Shiny CRT Calculator (Web-based) 59 |
Hussey and Hughes18 |
| Linear mixed model (random cluster-by-time interaction) |
swCRTdesign (R)
74
swdpwr (R) 61 SteppedPower (R) * %swdpwr (SAS macro) 61 Shiny CRT Calculator (Web-based) 59 |
Hooper et al.22 | ||
| Linear mixed model (exponential decay) | Shiny CRT Calculator (Web-based) 59 | Kasza et al.21 | ||
| Linear mixed model (random intervention) | swCRTdesign (R) 74 | Hughes et al.26 Hemming et al.27 |
||
| GEE (nested exchangeable correlation structure) |
swdpwr (R)
61
%swdpwr (SAS macro) 61 |
Li et al.36 | ||
| Closed-cohort | Linear mixed model (random cluster-by-time interaction) |
swdpwr (R)
61
%swdpwr (SAS macro) 61 Shiny CRT Calculator (Web-based) 59 |
Hooper et al.22 | |
| GEE (block exchangeable correlation structure) |
swdpwr (R)
61
%swdpwr (SAS macro) 61 |
Li et al.36 | ||
| GEE (proportional decay correlation structure) | SteppedPower (R) * | Li41 | ||
| Open-cohort | Linear mixed model (random cluster-by-time interaction or exponential decay) | SteppedPower (R) * | Kasza et al.58 | |
| Binary | Cross-sectional | Linear mixed model approximation |
swCRTdesign (R)
74
SWSamp (R) 75 steppedwedge (Stata) 76 Shiny CRT Calculator (Web-based) 59 |
Hussey and Hughes18 |
| Linear probability mixed model (random intercept) |
swdpwr (R)
61
%swdpwr (SAS macro) 61 |
Zhou et al.60 | ||
| GEE (nested exchangeable correlation structure) |
swdpwr (R)
61
%swdpwr (SAS macro) 61 |
Li et al.36 | ||
| GEE (exponential decay correlation structure) | Available on GitHub or Journal website † | Harrison and Wang38 Tian et al.39 |
||
| Closed-cohort | GEE (block exchangeable correlation structure) |
swdpwr (R)
61
%swdpwr (SAS macro) 61 |
Li et al.36 |
*
The SteppedPower R package is available on The Comprehensive R Archive Network (CRAN) at https://cran.r-project.org/web/packages/SteppedPower/index.html
†
The code for sample size estimation with exponential decay correlation structure can be found in https://github.com/lindajaneharrison/SW-CRTs/releases/tag/v2.0 for Harrison and Wang38, and in https://github.com/Zebedial/SWD-variable-cluster-sizes or https://onlinelibrary.wiley.com/doi/full/10.1002/bimj.202100112 for Tian et al.39