Question

Analysts at the Milk Company calculated the average price of a gallon of its milk over 10 years. The following table shows the years since 2010 and the average price of a gallon of milk at that time.

Years (since 2010) 0 1 2 3 4 5 6 7 8 9
Price (in dollars) 3.26 3.57 3.49 3.46 3.69 3.42 3.20 3.23 2.90 3.04

Which of the following representations is most appropriate for showing how the price changed each year?
A: scatter plot titled gallon of milk, with the x axis labeled years since 2010 and the y axis labeled price in dollars with points at 0 comma 3.26, 1 comma 3.57, 2 comma 3.49, 3 comma 3.46, 4 comma 3.69, 5 comma 3.42, 6 comma 3.20, 7 comma 3.23, 8 comma 2.90, and 9 comma 3.04
B: line graph titled gallon of milk, with the x axis labeled years since 2010 and the y axis labeled price in dollars with points at 0 comma 3.26, 1 comma 3.57, 2 comma 3.49, 3 comma 3.46, 4 comma 3.69, 5 comma 3.42, 6 comma 3.20, 7 comma 3.23, 8 comma 2.90, and 9 comma 3.04
C: line graph titled gallon of milk, with the y axis labeled years since 2010 and the x axis labeled price in dollars with points at 3.26 comma 0, 3.57 comma 1, 3.49 comma 2, 3.46 comma 3, 3.69 comma 4, 3.42 comma 5, 3.20 comma 6, 3.23 comma 7, 2.90 comma 8, and 3.04 comma 9
D: scatter plot titled gallon of milk, with the y axis labeled years since 2010 and the x axis labeled price in dollars with points at 3.26 comma 0, 3.57 comma 1, 3.49 comma 2, 3.46 comma 3, 3.69 comma 4, 3.42 comma 5, 3.20 comma 6, 3.23 comma 7, 2.90 comma 8, and 3.04 comma 9

Answer 1

Explanation:

The representation that is the most appropriate for showing how the price changed each year is given by:

The second graph.

How to choose the correct graph?

There are two steps to identify the correct graph, as follows:

Obtain the input and the output variable.

Classify the input variable as discrete or continuous.

The input and the output variables are given as follows:

Input variable: Number of years since 2010.

Output variable: Price of the gallon of milk.

As the input variable is graphed on the horizontal axis, while the output variable is graphed on the vertical axis, the first and the fourth graphs are incorrect, as they have each variable on the wrong axis.

The price keeps changing throughout the years, that is, the price does not remain constant throughout the year, meaning that the domain is continuous, and thus the graph is composed by a solid line.

This means that the second graph is the correct graph in this problem. (the solid, approximately horizontal line).