Question

Tim is investigating the relationship between the number of years since a tree was planted and the height of the tree in feet. His data are shown in the table.
Years Since Tree was Planted vs. Height of Tree
Years since tree was planted, x
Height of tree in feet, y
2
17
3
25
5
42
6
47
7
54
9
69

Using a regression calculator, what is a good prediction for the height of the tree when it is 100 years old?

A calculator screen. A 2-column table with 6 rows titled Data. Column 1 is labeled x with entries 2, 3, 5, 6, 7, 9. Column 2 is labeled y with entries 17, 25, 42, 47, 54, 69. The regression equation is y almost-equals 7.36 x + 3.08; r almost-equals 0.998.
A good prediction for the height of the tree when it is 100 years old is about 315 feet because that is what the trend line, y almost-equals 3.08 x + 7.36, produced by the regression calculator predicts.
A good prediction for the height of the tree when it is 100 years old is about 739 feet because that is what the trend line, y almost-equals 7.36 x + 3.08, produced by the regression calculator predicts.
There is not a good prediction for the height of the tree when it is 100 years old because the trend line produced by the regression calculator does not give a prediction.
There is not a good prediction for the height of the tree when it is 100 years old because the prediction given by the trend line produced by the regression calculator probably is not valid that far in the future.

Answer 1

Answer: There is not a good prediction for the height of the tree when it is 100 years old because the prediction given by the trend line produced by the regression calculator probably is not valid that far in the future.

Step-by-step explanation:

Years since tree was planted (x) - - - - height (y)

2 - - - - 17

3 - - - - 25

5 - - - 42

6 - - - - 47

7 - - - 54

9 - - - 69

Using a regression calculator :

The height of tree can be modeled by the equation : ŷ = 7.36X + 3.08

With y being the predicted variable; 7.36 being the slope and 3.08 as the intercept.

X is the independent variable which is used in calculating the value of y.

Predicted height when years since tree was planted(x) = 100

ŷ = 7.36X + 3.08

ŷ = 7.36(100) + 3.08

y = 736 + 3.08

y = 739.08

Forward prediction of 100 years produced by the trendline would probably give an invalid value because the trendline only models a range of 9 years prediction. However, a linear regression equation isn't the best for making prediction that far in into the future.