The median is the value that is in the middle of a dataset.
The first step to find the median is to order the values from least to greatest:
7, 8, 11, 12, 13, 15.
Since the number of data is even, the median will be the average of the pair of values that is in the middle, in this case, 11 and 12:
The median of the data set is 11.5.