5. Let us apply the formula to some numbers. The following are the durations in minutes of a series of telephone calls. You want to know the mean duration of the calls.

µ ═ ∑ X
n

Duration of calls: 12.3, 18.2, 33.1, 9.1, 7.3, 10.4, 11.5, 4.5, 8.9, 3.3