1. In the United States, men have been shown to have greater age-related hearing loss than women have.

One explanation for this is that men tend to work around noisy machinery more often than women do. To test the idea that for humans, working around noisy machinery is related to age-related hearing loss, you would want to use which of the following research designs?

a. An experiment

b. A correlational design

c. A naturalistic observation

d. A case study