Which is the greatest, the mean, the mode, or the median of the data set?11; 11; 12; 12; 12; 12; 13; 15; 17; 21; 21; 21the meanthe mode    the median

To answer this question, we first need to calculate the mean, mode, and median of the given data set.

The data set is: 11, 11, 12, 12, 12, 12, 13, 15, 17, 21, 21, 21

1. Mean: The mean is the average of all numbers in the data set. We calculate it by adding all numbers and then dividing by the count of numbers.

   (11+11+12+12+12+12+13+15+17+21+21+21) / 12 = 15.75

2. Mode: The mode is the number that appears most frequently in a data set. In this case, the mode is 12, as it appears four times.

3. Median: The median is the middle number in a sorted, ascending or descending, list of numbers. If there is an even number of observations, the median is the average of the two middle numbers.

   In this case, the sorted list is: 11, 11, 12, 12, 12, 12, 13, 15, 17, 21, 21, 21. The two middle numbers are 12 and 13, so the median is (12+13)/2 = 12.5

Comparing these three values, the greatest is the mean, which is 15.75.