A group of 15 rats running a straight-alley maze required the following number of trials to perform at a predetermined criterion level: Trials required to reach criterion: 18 19 XXXXXXXXXX Number of...

A group of 15 rats running a straight-alley maze required the following number of trials to perform at a predetermined criterion level:

Trials required to reach criterion: 18 19 20 21 22 23 24

Number of rats (frequency): 1 0 4 3 3 3 1

Calculate the mean and median of the required number of trials for this group