Our first example comes from the United Nation's World Development Indicators, a source we've used before. In this instance, we'll look at the variation in the birth rate around the world. Specifically, birth rate is defined as the number of births annually per 1,000 population. We'll initially ask if differences in birth rates are associated with one particular matter of public policy: whether maternity leave is provided by the state, by the private sector, or by a combination of public and private sectors.
Note that this is observational data, so that we have not established the different factor levels experimentally or by design. Open the Birthrate 2005 data table.
We'll start simply by examining the distribution of the response ...