Question

Timothy downloaded 10 files to his computer. The scatter plot below shows the relationship between the size of the file and the amount of time needed to download.

The graph titled Downloading files shows Time in seconds on y-axis and size in megabytes on x-axis. There are dots at (5, 30), (5, 40), (10, 37), (10, 50), (20, 50), (22, 57). (25, 75), (30, 75), (35, 87), and (37, 75).

To represent the data, Timothy drew a line through the points (0,50) and (40,75). Which statement explains why his line is not the line of best fit for the data?

A.
Timothy’s line is more vertical than it should be, and most of the points are too far away from the line.

B.
Most of the data points lie above Timothy’s line.

C.
Timothy’s line is more horizontal than it should be, and most of the points are too far away from the line.

D.
Most of the data points lie below Timothy’s line.

Answer 1

D.

Timothy’s line through (0,50) and (40,75) has equation y = 0.625x + 50. For the points (5,30),(5,40),(10,37),(10,50),(20,50),(22,57) the line predicts larger y-values, so those six points lie below the line, while only four points lie above it. Thus most data points lie below his line.