Question 408052
4  5  5  7  8  9  9  9  9  12  14  16  16  16  17  18  21  21  25

Mean is 241/19 = 12.68421, to 5 decimal places.
Median is the 10th entry, 12
Mode is 9.
Midrange is (4 + 25)/2 = 14.5
The 1st quartile is between the 4th and 5th terms: (7+8)/2 = 15/2 = 7.5.
The 3rd quartile is between the 14th and 15th terms: (16+17)/2 = 16.5.
The 1st quartile 7.5 separates the lowest 25% of the distribution from the rest.
The 3rd quartile 16.5 separates the highest 25% of the distribution from the rest.