Melatonin is compared to placebo for sleep in a single-group…

Melatonin is compared to placebo for sleep in a single-group randomized cross-over study (n=328). Participants are randomized to receive melatonin or placebo for 3 months and then take the other agent for 3 months following a 1-week washout period. Which of the following tests would be most appropriate to determine if this is a statistically significant difference in mean sleep latency (i.e., mean minutes to fall asleep)?