Q18
12 marks
Linear regression
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(12 points)
The figure below is a line graph of environmental infrastructure investment $y$ (in units of 100 million yuan) from 2000 to 2016 in a certain region.
To forecast the environmental infrastructure investment for 2018 in this region, two linear regression models were established for $y$ and time variable $t$. Based on data from 2000 to 2016 (time variable $t$ takes values $1, 2, \ldots, 17$ respectively), Model (1) is established: $\hat { y } = - 30.4 + 13.5 t$; based on data from 2010 to 2016 (time variable $t$ takes values $1, 2, \ldots, 7$ respectively), Model (2) is established: $\hat { y } = 99 + 17.5 t$.
(1) Using each of these two models respectively, predict the environmental infrastructure investment for 2018 in this region;
(2) Which model do you think gives a more reliable prediction? Explain your reasoning.