Bluebook SAT Test Two-Variable Data: Models and Scatterplots 14

Question 1

A line of best fit is described by y = 4x + 8. Which data point lies BELOW the line?

Accepted Answer

(3, 18)

Answer

At x=3, predicted y = 4(3)+8 = 20; actual y=18 < 20, so this point is below the line.

Question 2

Data on price (x, dollars) and quantity demanded (y, units) gives the line y = −50x + 1000. What quantity is demanded when price is $12?

Accepted Answer

400 units

Answer

y = −50(12)+1000 = −600+1000 = 400 units.

Question 3

A researcher collects data and finds that first differences of y are NOT constant, but second differences ARE constant. What type of model best fits?

Accepted Answer

Quadratic

Answer

Constant second differences indicate a quadratic relationship between x and y.

Question 4

A model for the height of a ball (y, meters) over time (x, seconds) is y = −5x² + 20x. When is the ball at its maximum height?

Accepted Answer

x = 2 seconds

Answer

x-coordinate of vertex: x = −b/(2a) = −20/(2·(−5)) = 20/10 = 2 seconds.

Question 5

The slope of a best-fit line for the data is calculated as 2. A second analyst calculates the slope as −2 using the same data. Which is more likely true?

Accepted Answer

One analyst likely made a calculation error, since a dataset has only one best-fit slope.

Answer

A given dataset has one unique least-squares best-fit line with a single slope; one analyst made an error.

Bluebook SAT Practice Test

Bluebook SAT Practice Test

Bluebook SAT Test Two-Variable Data: Models and Scatterplots 14