In a certain noisy factory, workers are provided with earplugs and are expected to wear them. An industrial hygienist inspecting the plant found that 100 of the 500 workers in the factory were not wearing their earplugs because they regarded them as uncomfortable and a nuisance. When all the workers were given a hearing test, it was found that 4 of the earplug wearers and 10 of the nonwearers had developed significant hearing loss. All had had normal hearing at their preemployment examinations 1 year earlier, when the plant opened
1. What was the cumulative incidence rate of hearing loss in workers who did not wear earplugs?
2. What was the relative risk of hearing loss in workers who did not wear earplugs, compared with those who did?
3. What was the risk of hearing loss attributable to not wearing earplugs? (i.e., what was the risk difference?)
4. What proportion of hearing loss in the nonwearers was attributable to not wearing earplugs?
5. What proportion of the hearing loss in all the workers was attributable to not wearing earplugs?