A company had 74 employees whose salaries are summarized in the frequency distribution below. Find the standard deviation. Find the standard deviation of the data summarized in the given frequency distribution.
Salary Number of Employees
5,001 -10,000 11
10,001 - 15,000 13
15,001 - 20,000 20
20,001 - 25,000 17
25,001 - 30,000 13