Quiz_Applications_of_Cubic_Functions_Part_2

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```					               QUIZ: Applications of Cubic Functions Part 2

The data in the table give the average speed y (in knots) of the Trident
motor yacht for several different engine speeds x (in hundreds of
revolutions per minute, or RPMs)

Engine Speed, x   Boat Speed, y
9              6.43
11              7.61
13              8.82
15              9.86
17              10.88
19              12.36
21.5             15.24

Create a scatterplot (Boat Speed vs. Engine Speed) of the data in Excel and
paste your graph below. Be sure to include a TITLE for your graph and
LABEL THE X AND Y AXES.

Find a quadratic regression model ( y  ax 2  bx  c ) for the data and
report the model below. What is the value of r-squared for this model?


Find a cubic regression model ( y  ax 3  bx 2  cx  d ) for the data and
report the model below. What is the value of r-squared for this model?



Which model is a better fit for the data? How do you know?

Estimate the average boat speed of the Trident for an engine speed of
2400 RPMs. (Hint: 2400 RPMs would equal an x value of 24 since the
equation denotes engine speed in hundreds of revolutions per minute.)

```
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