The mode of the data of sample with 15 values is c) 17.
The mode of any sample of data can be calculated by finding the number that is present highest number of times. Based on this, we will look for the numbers that are present multiple times in the mentioned sample.
17, 18 and 5 are the three numbers that are present more than once. Now, let's see what is the frequency of each of these numbers.
Frequency of 17 - 4
Frequency of 18 - 2
Frequency of 5 - 2
Thus, the number 17 is present maximum number of times and hence is the mode of the data.