A newspaper editor wants to investigate whether the residents of two counties support the proposal to build a wind farm. She plans to take an SRS of 30 residents from the southern county and 40 residents from the
northern county, then look at the difference (southern - northern) between the proportions of residents
that support the proposal in each sample. Suppose that 65% of the residents of the southern county and 52%
of the residents of the northern county approve.
What are the mean and standard deviation of the sampling distribution of the difference in sample
proportions?