As an aid to the establishment of personnel requirements, the director of a hospital wishes to estimate the mean number of people who are admitted to the emergency room during a 24-hour period. The director randomly selects 81 different 24-hour periods and determines the number of admissions for each. For this sample, the mean number of people was 396, and the standard deviation was 63. Estimate the mean number of admissions per 24-hour period with a 99% confidence interval.