Parameter | Number of scenarios | Values |
---|---|---|
Total number of clusters | 4 | 8, 12, 20, 30 |
Mean Cluster size (\(\overline{{\varvec{m}} }\)) | 3 | 10, 50, 1000 |
Coefficient of variation (CV) of cluster size | 3 | \(CV=\frac{s}{\overline{m} }= 0, 0.5, 0.8\) Where s is the standard deviation in cluster sizes and\(\overline{m }\)is the mean cluster size, Cluster size \({m}_{ij}\)is sampled from a negative binomial distribution as follows: \(\delta \sim Negbin\left(no of fails=\frac{{(\overline{m }-2)}^{2}}{{s}^{2}-(\overline{m }-2)},p of fail=\frac{\overline{m }-2}{{s}^{2}}\right)\) \({m}_{ij}=2+\delta\)Â Â |
Control cluster prevalence | 2 | 10%, 30% |
Intervention effect | 2 | No effect, or odds ratio between 1.12 and 11.49 selected for each scenario to achieve 80% power |
ICC | 4 | 0.001, 0.01, 0.05, 0.1 |
Cluster effect distribution | 3 | Normal: \({u}_{ij}\sim N(0,{\sigma }_{b}^{2})\) Gamma \({u}_{ij}=\frac{{\sigma }_{b}\left({a}_{ij}-2\right)}{\sqrt{2}}\)where \({a}_{ij}\sim Gamma\left(\mathrm{2,1}\right)\) Uniform \({u}_{ij}\sim Uniform\left(-\sqrt{3{\sigma }_{b}^{2}},\sqrt{3{\sigma }_{b}^{2}}\right)\) Distributions are defined to give the specified between cluster variability set by the ICC |