Table 14.4.3 shows the quarterly net sales of Mattel, a major designer, manufacturer, and marketer of toys. Because of seasonal gift giving, you might expect fourth-quarter sales to be much higher, generally, than those of the other three quarters of the year.
a. Construct a time-series plot for this data set. Describe any trend and seasonal behavior that you see in the plot.
b. Calculate the moving average (using one year of data at a time) for this time series. Construct a time-series plot with both the data and the moving average.
c. Find the seasonal index for each quarter. Do these values appear reasonable when you look at the time-series plot of the data?
d. Which is Mattel’s best quarter (1, 2, 3, or 4)? On average, how much higher are sales as compared to a typical quarter during the year?
e. Find the seasonally adjusted sales corresponding to each of the original sales values.
f. From the third to the fourth quarter of 2007, sales went up from 1,838.574 to 2,188.626. What happened on a seasonally adjusted basis?
g. From the second to the third quarter of 2007, Mattel’s sales rose considerably, from 1,002.625 to 1,838.574. What happened on a seasonally adjusted basis?
h. Find the regression equation to predict the longterm trend in seasonally adjusted sales for each time period, using 1, 2,…for the X variable.
i. Compute the seasonally adjusted forecast for the fourth quarter of 2009.
j. Compute the forecast for the fourth quarter of 2009.
k. Compare the forecast from part i to Mattel’s actual net sales of 1,955.128 for the fourth quarter of 2009. Is your result consistent with the possibility that the recession from December 2007 through June 2009 might have disrupted the sales pattern?

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