1) x = avg # of employees in group health insurance plan

y = avg. admin. Cost as percentage of claims

x: 3 7 15 35 75

y: 40 35 30 25 18

a) Make a scatterplot.

b) Would you say that the data points: closely fit a straight line; loosely fit a straight line; or, do not appear to have a straight-line pattern at all?

c) Describe the apparent correlation in terms of strength (strong, weak, or moderate) and direction (positive or negative).

d) Calculate the value of r. What kind of correlation does it describe?

e) Company A has 20 employees in its group health plan, while company B has 60. Which company probably has the lower administrative costs as a percentage of claims? Explain.

2) x = magnitude of earthquake on Richter scale

y = depth (km) of quake below surface

x: 2.9 4.2 3.3 4.5 2.6 3.2 3.4

y: 5.0 10.0 11.2 10.0 7.9 3.9 5.5

a) Make a scatterplot.

b) Would you say that the data points: closely fit a straight line; loosely fit a straight line; or, do not appear to have a straight-line pattern at all?

c) Describe the apparent correlation in terms of strength (strong, weak, or moderate) and direction (positive or negative).

d) Calculate the value of r. What kind of correlation does it describe?

e) Do more severe earthquakes tend to occur closer to the surface than milder ones, or deeper down? Explain.

f) Using the data given, would it be possible to give a close, reliable estimate of the depth of a magnitude 3.1 earthquake? Explain.

3) x = student enrollment (in thousands) on a university campus

y = # of burglaries per year on the campus

x: 12.5 30.0 24.5 14.5 7.5 27.7 16.2 20.1

y: 26 73 39 23 15 30 15 25

a) Make a scatterplot.

b) Would you say that the data points: closely fit a straight line; loosely fit a straight line; or, do not appear to have a straight-line pattern at all?

c) Describe the apparent correlation in terms of strength (strong, weak, or moderate) and direction (positive or negative).

d) Calculate the value of r. What kind of correlation does it describe?

e) Do larger universities tend to have more property crimes? If so, is this solely because of the number of students, or are other factors likely to be involved? Explain.