sscsample.data
(Package: Bolstad) :
Data for simple random sampling, stratified sampling, and clusting sampling
A simulated population made up of 100 individuals. The individuals come from three ethnic groups with population proportions of 40%, 40%, and 20%, respectively. There are twenty neighborhoods, and five individuals live in each one. Now, the income distribution may be different for the three ethnic groups. Also, individuals in the same neighborhood tend to be more similar than individuals in different neighborhoods.
providing 
.