13.2. Table 9.13 on page 294 showed data for several nations on various indices. Let y = percentage who use the Internet, x = per capita GDP (in thousands of dollars), and z = whether the nation is a Western nation (1 = yes, 0 = no).

(a) The prediction equation for the effect of z is y = 10.5 + 30.4z. Interpret the coefficients.

(b) The prediction equation for the effects of x andzisy = 8.3 + 0.73x + 10.9z. Interpret the coefficients.

(c) Explain how the coefficient of z could be so different in

(a) and (b).