Data from Sweden indicates that there is a strong correlation between the number of storks (a type of bird) and the number of babies born.We know that more storks live in the urban areas than in the rural areas.

a)Draw a three-variable diagram to show the relationship between the number of storks, the number of babies born, and region (rural vs. urban).

b)If we control for the effect of region, what will happen to the correlation between the number of stork and the number of babies born?

We hypothesize that "percentage of residents supporting for a law to register handguns" (Y) depends on "size of community of residence" (X₁), measured as the number of residents, and "percentage of residents own guns" (X₂).According to a sample of 400 neighborhoods, the following statistics are found: b₁ = .05, b₂ = -.33, a = 15.50.

c) Write the prediction equation.

d)What is the expected percentage of resident who support for a law to register handguns for a neighborhood of 1,000 residents and 20 percent of its residents own guns.

e) Show that the relationship between Y and X₂ for neighborhoods of 500 residents is E(Y) = 40.50-.33X₂.