Data:
15, 15, 16, 16, 16, 17, 17, 18, 19

Solution:
The mean is defined as, the sum of the values divided by the number of values.
The mean of the above data set is given as,
=15+15+16+16+16+17+17+18+19/9
=149/9
=16.556

Median:
The middle value of an arranged data set is called median.
Arranged data means writing the values in ascending order. The given values in ascending order are given as:
15, 15, 16, 16, 16, 17, 17, 18, 19 (already in ascending order)
Hence, the median of the above data set is given as
15+15+16+16+16+17+17+18+19
Median = 16

Mode:
The mode is the most repeated value in a data set.
The most repeated value in the given data is 16.
So, Mode = 16

Range:
Range is the difference between the largest value and the smallest value.
In the given data set the largest value is 19, and the smallest value is 15. Hence,
Range = 19 − 15 = 4