FILE Consider the following table, consisting of 20 observations of the variable y and tim e t. The data are also on the text website, labeled Exercise 18.11.

t y

t y t

y t

y 1 3.01 6 4.94 11 7.28 16 14.16 2 3.13 7 6.10 12 9.04 17 14.85 3 4.19 8 5.91 13 9.49 18 16.77 4 5.07 9 6.56 14 12.12 19 18.07 5 4.46 10 7.29 15 13.15 20 19.99

a. Plot the series along w ith the superimposed linear and exponential trends. Which trend model do you think describes the data well?

b. Estimate a linear trend model and an exponential trend model for the sample. Validate your guess from the graphs by comparing the MSE and MAD.