An audiologist is interested in the efficacy of three different types of hearing aids. He gathers three groups of hearing-impaired clients: One group receives analog hearing aids, which convert sound waves into amplified electrical signals.
The second group receives digital hearing aids, which use directional microphones to control the flow of sound and convert the sound waves into numerical codes before amplifying them.
The third group receives cochlear implants. The results come in, and a statistician conducts an analysis of variance.

Required:
In this study what is the hearing aid type considered and What are the treatments (analog hearing aids, digital hearing aids, and cochlear implants) considered?