The plastics data set consists of the monthly sales (in thousands) of product A for a plastics manufacturer for five years. a. Plot the time series of sales of product A. Can you identify seasonal...

The plastics data set consists of the monthly sales (in thousands) of product A for a plastics manufacturer for five years.

a. Plot the time series of sales of product A. Can you identify seasonal uctuations and/or a trend-cycle?

b. Use a classical multiplicative decomposition to calculate the trend-cycle and seasonal indices.

c. Do the results support the graphical interpretation from part a?

d. Compute and plot the seasonally adjusted data.

e. Change one observation to be an outlier (e.g., add 500 to one observation), and recompute the seasonally adjusted data. What is the eect of the outlier?

f. Does it make any dierence if the outlier is near the end rather than in the middle of the time series?