An education researcher measured the IQ test scores of 78 seventh-grade students in a rural school, and also their school grade point average (GPA) measured on a 12-point scale. Here is a graph of GPA versus IQ for these students: One of these numbers is the correlation r between IQ score and GPA. Which is it?
A) r = 0.02
B) r = 0.63
C) r = 0.95
D) r = -0.63
E) r = -0.95

Question

An education researcher measured the IQ test scores of 78 seventh-grade students in a rural school, and also their school grade point average (GPA) measured on a 12-point scale. Here is a graph of GPA versus IQ for these students:  One of these numbers is the correlation r between IQ score and GPA. Which is it?
A) r = 0.02 
B) r = 0.63 
C) r = 0.95 
D) r = -0.63 
E) r = -0.95

Quizplus · Accepted Answer

The scatterplot shows a clear positive linear relationship between IQ and GPA, with higher IQ scores corresponding to higher GPAs. Therefore, the correlation r should be positive. Looking at the scatterplot, r seems to be fairly strong, since the points are tightly clustered around the line of best fit. Option B, r = 0.63, is the closest to the correlation coefficient that matches this trend. Options A, C, D, and E have correlations that are too weak or too strong compared to the scatterplot.

An Education Researcher Measured the IQ Test Scores of 78