Kiara made the table below to show the IQ scores and grade point averages (GPAs) of students in her class. She made another table to show the standardized test scores and IQ scores.



IQ, GPA, and SAT Scores
IQ
GPA

IQ
Standardized Test Score
120
3.7

120
1540
85
2.3

85
800
110
3.0

110
1,200
96
2.7

96
1000
100
2.9

100
1100

She graphs the data in each table and writes the rounded values as shown for the regression line y = a x + b.

I Q and G P A. a = 0.04. b = negative 0.9. I Q and Standardized Scores. A = 20. b = negative 924.


Next, Kiara uses the steps below to predict a student’s standardized test score based on the student’s GPA of 4.0.

Step 1 Write the equation of the trend line for IQ and GPA.
y = 0.04 x minus 0.9
Step 2 Write the equation of the trend line for IQ and standardized test score.
y = 20 x minus 924
Step 3 Find the IQ that is expected from a GPA of 4.0.
y = 0.04 x minus 0.9. 4 = 0.04 x minus 0.9. 4.9 = 0.04 x. 122.5 = x.
The IQ is about 122.5.
Step 4 Find the corresponding standardized test score for an IQ of 122.5.
122.5 = 20 x minus 924. 122.5 = 20 x minus 924. y = 523.
The standardized test score is 523.

In which step did Kiara make the first error?
step 1
step 2
step 3
step 4
Mark this and return