A two-arm randomized controlled trial is being planned in which participants will be randomly assigned to use a soothing sound machine during sleep or to a control group that continues with their normal sleep routine. The continuous response variable will be a composite score of sleep quality that ranges from 0 to 50. The investigators have specified the variance of the composite sleep quality measure to be 30 units for both groups. What sample size is needed per group to detect a difference in mean composite sleep quality score of at least 5 units with a 95% confidence level ( = 0.05) and 80% power