Question

You research the average cost of whole milk for several recent years to look for trends. The table shows your data. What is the equation for a line of best fit? How much would you expect to pay for a gallon of whole milk in the year 2023

Answer 1

The correct answers are:

y = 0.10x + 2.50; $5.

Explanation:

Using a graphing calculator, we enter the data in the STAT function. The year will be the independent (x) variable and the cost will be the dependent (y) variable.

For the year, instead of starting at 1998, we will start at 0, since that is where we started measuring. This means the year 2000 will be 2; 2002 will be 4; etc, up to x=10.

Running the linear regression, the calculator gives us a slope of 0.10 and a y-intercept of 2.499, or 2.50. This makes the equation y = 0.10x + 2.50.

To predict the price in 2023, we first find what our x-value will be. Subtract 1998 from this:

2023-1998 = 25

Now substitute 25 in place of x in the equation:

y = 0.10(25) + 2.50 = 2.50 + 2.50 = 5