518 Figure 59 below is a scatterplot of school GPA against I

(5.18) Figure 5.9 (below) is a scatterplot of school GPA against IQ test scores for 15 seventh-grade students. The line is the least-squares regression line for predicting school GPA from IQ score. If another child in this class has IQ score 110, you predict the school GPA to be close to
	A. 2 B. 7.5 C. 11

(5.18) Figure 5.9 (below) is a scatterplot of school GPA against IQ test scores for 15 seventh-grade students. The line is the least-squares regression line for predicting school GPA from IQ score. If another child in this class has IQ score 110, you predict the school GPA to be close to A. 2 B. 7.5 C. 11 22. (5.19) The slope of the line in Figure 5.9 (shown below) is closest to A. -11. B. 0.2. C. 2.0.

Solution

First question: Answer B. 7.5. Go over to 110 on the bottom axis, which is the IQ score and draw a straight line up to the red line. The value on the vertical axis at this point is between 7 and 8, so the answer is B, 7.5.

Second question: Answer B. 0.2. You can compute the slope by picking two points on the line, such as (90, 4) and (130, 11) and using the slope formula.

The slope is the difference in the Y values divided by the difference in the x values:

(11-4)/(130-90) = 7/40 = .175. This is closes to B, .2.