A walk-in clinic for emergency room services maintains records of the number of patients it treats per day. The following table shows the frequency of the patient arrivals over the course of a 150-day period:

Number of Patients per Day Frequency 20 to under 40 10 40 to under 60 16 60 to under 80 25 80 to under 100 65 100 to under 120 34

a. Calculate the approximate average number of patients per day.

b. Calculate the approximate variance and standard deviation of the number of patients per day.

AppendixLO1