A pharmaceutical company asks 30 patients with acne to volunteer for an experiment in which they will receive treatment either a special medical lotion or normal moisturizing cream. What type of?

This is an example of a randomized controlled trial. The patients are randomly assigned to one of two groups: the treatment group, which receives the special medical lotion, or the control group, which receives the normal moisturizing cream. This design helps to ensure that any differences between the two groups are due to the treatment and not to other factors.