Question

Tanica drew a line of best fit on a scatterplot, as shown below. The equation of the line is y=-1.02x+7.09 Using the line, she predicted that when the value of x is 0.5, the value of y will be approximately 7.6. What was her mistake?

A.She drew the line of best fit incorrectly.

B.She used the line of best fit to predict y for an incorrect value of x.

C.She forgot the minus sign before the first term on the right side of the equation when she predicted y.

D.She plugged 0.5 into the equation for y instead of x and actually predicted x instead of y.

Answer 1

C-She forgot the minus sign before the first term on the right side of the equation when she predicted y.

Explanation:

I took just took the test and looked at the answer.

Answer 2

Her mistake was forgetting that the slope is -1.02. She used (positive) 1.02 instead, leading to y = 1.02x + 7.09 = 1.02(0.5) + 7.09 = 0.51 + 7.09 = 7.6. The correct answer is C.

The line on the graph is drawn correctly, and the value of x is given as correct. If she had set y = 0.5 instead of x = 0.5, she would have come up with x = 6.46.