Non-stratified data including 3 variables: id, z, group. Have some missing values.
A data frame with 340 observations on 3 variables.
[, 1] id cluster id
[, 2] z score
[, 3] group group id
https://sites.google.com/a/channing.harvard.edu/bernardrosner/channing/incorporating-cluster-effects-for-the-wilcoxon-rank-sum-test-1/cluswilcox/sample_data