The information below is the number of daily emergency service calls made by the volunteer ambulance service of Walterboro, South Carolina, for the last 50 days. To explain, there were 22 days on which there were 2 emergency calls, and 9 days on which there were 3 emergency calls. Number of Calls Frequency 0 8 1 10 2 22 3 9 4 1 Total 50 What is the standard deviation of the number of calls made daily.