The mean deviation of a set of numbers is the average of the absolute differences between each number and the mean of the set. To calculate the mean deviation of the set of numbers 7, 3, 14, 9, 7, and 8, we first need to find the mean of the set. The sum of the numbers is 7 + 3 + 14 + 9 + 7 + 8 = 48, and there are 6 numbers in total, so the mean is 48/6 = 8.

Next, we calculate the absolute differences between each number and the mean:

|7 - 8| = 1

|3 - 8| = 5

|14 - 8| = 6

|9 - 8| = 1

|7 - 8| = 1

|8 - 8| = 0

The sum of these absolute differences is 1 + 5 + 6 + 1 + 1 + 0 = 14, so the mean deviation is 14/6 = 7/3.