Pranalee was practicing for a 100 m running race.
She ran 100 m distance 20 times. The time required, in seconds, for each attempt was as follows.
18, 17, 17, 16,15, 16, 15, 14,16, 15, 15, 17, 15, 16,15, 17, 16, 15, 14,15
Find the mean of the time taken for running.
