PSAT Math Multiple-Choice Question 494: Answer and Explanation

Question: 494

A data set showing the relationship between two variables is graphed in the xy-plane to produce the scatterplot below. A line of best fit is generated and is shown on the graph.

How much greater is the y-value of the data point at x = 4 than the y-value of the best fit line at the same x-value?

• A. 12.5
• B. 6.5
• C. 6.0
• D. 0.5

Correct Answer: D

Explanation:

D

The question asks for the difference between two values on a graph. The x-values are listed along the horizontal axis, so find 4 on that axis. From this point, trace up to find the intersection with the line of best fit, using the answer sheet as a straight edge if necessary. Trace left to find that this corresponds with 6 on the y-axis. Now, find the dot for the data point at x = 4 just above the line and trace left to find the y-value on the vertical axis. This is halfway between 6 and 7 on the y-axis, or 6.5. The difference is 6.5 – 6 = 0.5. The correct answer is (D).