CS&SS/SOC/STAT 221: Quiz 3
May 7, 2015
VERSION: A - solution
Correlation
Question 1
A student was studying the relationship between how much money students spend on food and
on entertainment per week. Based on a sample size of 270, he calculated a correlation
coefficient (r) of .013 for these two variables. Which of the following is an appropriate
interpretation?
a. This low correlation of .013 indicates there is no relationship.
b. There is no linear relationship but there may be a nonlinear relationship.
c. This correlation indicates there is some type of linear relationship.

For Questions 2 – 5, consider the five scatterplots that are shown below in Figure 1:
Question 2
For which plot in Figure 1 would correlation be an
inappropriate
summary of the relationship
between x and y?

Question 3
Based on the scatterplots in Figure 1, in which plot do x and y have a correlation (r) of 0.9?

1

Question 4
Looking only at scatter plots 1 – 3 and 5 in Figure 1, in which plot do x and y have a correlation
of 0?

Question 5
Based on the scatter plots in Figure 1, in which plot there is the strongest linear relationship
between x and y?
a. plot 1
b. plot 2
c. plot 3
d. plot 4
e. plot 5

2
Regression
The following scatter plot displays the relationship between husbands’ and wives’ ages in a
random sample of 170 married couples in Britain, where both partners’ ages are below 65
years.