Problem: Dr. Kline, an environmental psychologist, conducts a study to examine whether visiting zoos causes people to have more positive attitudes toward environmental conservation. He asks a group of 45 people attending the zoo on a Saturday morning about their attitudes. He finds that 69% of the people report having a positive attitude after their visit. Which of the following is true?
a. His control group is people who did not visit the zoo.
b. He does not have a dependent variable.
c. He can make a strong causal claim about the effect of zoo visits on environmental attitudes.
d. His study does not qualify as an experiment.