I need help with part c

1. A study of sick-leave days over one year for a sample of 20 workers in a company yields the following numbers, arranged in increasing order: HEII-m (a) What is the sample mean of this data? The median? (b) Verify that the sample stande deviation is 7.27. (c) What proportion of the observations actually falls within one standard deviation of the mean? What aspect of the data explains the discrepancy between this fraction and the Empirical Rule approximation