The table shows the average cost of gasoline in the United States in dollars per gallon for the given years.

Year 1995 1996 2000 2001 2005 2006 2010 2011 2013 2014
Price per gallon ($) 1.13 1.14 1.33 1.49 1.88 2.36 2.77 3.15 3.39 3.40


(a) Write the least squares regression equation that models the data. Let x = time in years since 1995 and let y = price per gallon.

(b) Use the equation to estimate the price per gallon in 2030. Show your work.

Respuesta :

From the given table, the year values, and prices, we have the following

equation and values;

(a) The least squares regression equation is; y ≈ 0.1316·x - 261.73

(b) The estimate of the price per gallon in 2030 is approximately $5.418

How can the equation and price be obtained from the table?

(a) The coefficients of the least squares regression formula are

presented as follows;

[tex]a = \mathbf{\overline y - b \cdot \overline x}[/tex]

[tex]b = \mathbf{\dfrac{\sum \left(x_i - \bar x\right) \times \left(y_i - \bar y\right) }{\sum \left(x_i - \bar x\right )^2 }}[/tex]

Entering the given values in MS Excel, we have;

[tex]\overline x[/tex]  = 2005.1

[tex]\overline y[/tex] = 2.204

[tex]b = \dfrac{56.456 }{428.9} \approx 0.1316[/tex]

a = 2.204 - 0.1316 × 2005.1 ≈ -261.73

The least squares regression equation is therefore;

  • [tex]\underline{y =0.1316\cdot x - 261.73}[/tex]

(b) In the year 2030, we have;

The price, y ≈ 0.1316 × 2030 - 261.73 = 5.418

In the year 2030, the price per gallon will be approximately $5.418

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