13.55 Number of iPhones sold globally.
Consider data on the quarterly global sales (in millions of dollars) of iPhones from the first quarter of 2012 to the third quarter of 2014. In Exercise 13.22 (page 677), you were asked to fit a trend-and-season model using regression.
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(a) 1.310, 1.020, 0.811, 0.824. (b) The seasonally adjusted sales data is increasing over time. (c) . The trend term is significant, . (d) For the fourth quarter of 2014: 37.085. For the first quarter of 2015: 60.693.