A study will be conducted to investigate whether there is a difference in pain relief for two brands of headache pills, N and P. Participants will be randomly assigned to one of two groups. One group will take
pill N when they experience a headache, and the other group will take pill P when they experience a
headache. Each participant will record the number of minutes it takes until relief from the headache is
felt. The mean number of minutes will be calculated for each group
Which of the following is the appropriate test for the study?