Question 1
The table shows the profit
y (in thousands of dollars) that a company made during a month when the price of its product was
x dollars per unit.

a.
Fit the model
y =
β0 +
β1x +
β2x2 + ε to the data and give the least squares prediction equation.
b.
Plot the fitted equation on a scattergram of the data.
c.
Is there sufficient evidence of downward curvature in the relationship between profit and price? Use

Question 2
Consider the data given in the table below.

a. | Plot the data on a scattergram. Does a quadratic model seem to be a good fit for the data? |
Explain.
b. | Use the method of least squares to find a quadratic prediction equation. |
c. | Graph the prediction equation on your scattergram. |