Refer to Examples 1 and 2. The collector of antique grandfather clocks knows that the price ( y ) received for the clocks increases linearly with the age (x1) of the clocks.

Moreover, the collector hypothesizes that the auction price ( y ) of the clocks will increase linearly as the number of bidders (x2) increases. Use the information on the MINITAB printout shown in Figure 2 to

a. Test the hypothesis that the mean auction price of a clock increases as the number of bidders increases when age is held constant (i.e., when b2 7 0 ). (Use a = .05. )

b. Find a 90% confidence interval for b1 and interpret the result.