Doctors are interested in seeing if lifting weights to alleviate back pain is effective. Twenty five volunteers are asked to rank their level of pain on a scale from one to ten. For the next two months, they then exercise for 2 months with a physical therapist. The volunteers focus on different weight lifting exercises that strengthen the back. Twenty five volunteers are again asked to rank their level of pain on a scale from one to ten. Was the amount of pain less after completing the exercises? What type of test would they conduct to test this claim?