First, it is usually a good idea to arrange your data in numerical order from lowest to highest. We can arrange this data set as follows:
2,4,8,9,12,14,14,16,17,19
Now that the data is properly arranged, we can easily calculate the median. The median is the middle number in the data set. For this set, since there are 10 numbers there is no clear middle. In this case we take the two middle values, add them together and divide by 2
12+14 = 26
20/2 = 13
The median value for this data set is 10.
mean and average are interchangeable terms. They are calculated by taking the sum of all data points and dividing by the number of data points. For this data set we have:
2+4+8+9+12+14+14+16+17+19 = 115
115/10 = 11.5
Both mean and median can be useful in different situations. In this situation for example the mean is much lower than the median because data points 2 and 4 are weighed less heavily. When you have data which has a few extremes that may not fairly represent the majority of the data it may be useful to use the median instead of the mean.