For Exercises 13.18 to 13.20, see pages 670–671; for 13.21 to 13.23, see page 677; for 13.24, see page 679.

Question 13.19

13.19 Monthly cable sales.

Refer to the computer output for the linear trend fit of Example 13.12 (pages 665–666).

  1. Test the null hypothesis that the regression coefficient for the trend term is zero. Give the test statistic, -value, and your conclusion.
  2. The series ended at . Provide forecasts for festoon cable sales for periods and .

13.19

(a) . The data show a significant non-zero trend term. (b) 314.907. 319.44.