For United Nations data on y = world population size (billions) between 1900 and 2010, the exponential regression model with x = number of years since 1900 gives

ˆy = 1.4193(1.014)x.

(a) Explain why the model fit corresponds to a rate of growth of 1.4% per year.

(b) Show that the predicted population size (i) doubles after 50 years, (ii) quadruples after 100 years.

(c) The correlation equals 0.948 between y and x and 0.985 between log(y) and x. Based on this, which model seems more appropriate?Why?