Question

During the first recitation class of the semester, a teaching assistant asked each of the 12 students in his statistics section to rate his or her math phobia on a scale from 0-10. Later, the TA paired those phobia ratings with the students' scores on their first exam. The data in the following table; graph the scatterplot in order to answer the questions that follow the table.

a. Do you expect a positive or negative correlation? Do you expect the magnitude of the correlation to be fairly low, rather high, or moderate?

b. What characteristics of the pattern that you can see in the scatterplot prevents the correlation from being very close to perfect?

Phobia rating (X) 5 1 5 7 0 1 3 8 5 10 6 2

Exam 1 (Y) 94 96 87 75 91 93 90 77 97 78 89 88

Answer 1

a)Correlation coefficient is -0.70934. (By using excel function CORREL)

I expect a negative correlation. I expect themagnitude of the correlation to be moderate.

b) The characteristics of the pattern that I can see in the scatterplot prevents the correlation from being very close to perfectis that many points are away from line not very close to the regression line.

y -1.711x + 95.47 R2 0.503 120 100 80 60 40 Linear (Y) 20 10 12