Explain what is meant by a spurious association, drawing a scatter diagram to illustrate.

(a) Illustrate using x1 = shoe size, x2 = age, and y = number of books one has ever read, for children from schools in Winnipeg, Canada.

(b) Illustrate using x1 = height, x2 = gender, and y =

annual income, for a random sample of adults. Suppose that, overall, men tend to be taller and have higher income, on the average, than females.