Please work form Test 2, section 4, #20

Sure. The sociologist 300 students from each school, and finds that 10 in each school have 4 siblings. Because the students are selected at random and there are enough of them (300 is totally a representative sample of 2-3000 students), we can conclude that the proportion of the 300 students that have 4 siblings should hold for the whole schools. So let’s use two proportions to draw some conclusions about the number of students at each school with 4 siblings.

Lincoln School:

Washington School:

So there you have it, looks like we expect 30 more students at Washington School to have 4 siblings than we do at Lincoln School.