Data Analysis Definitions

Here are some of the most frequently used terms relating to data analysis:

MEAN
The mean is the numerical average of the data set. It is found by adding the numbers in the
data set together and dividing the sum by the number of data pieces in the set.

Ex. Lets say that I have 8 students.  The ages of my students are 5,7,8,12,15,11,9,13
First, I add all of the ages together.  The answer is 80.  Next, I divide 80 by the number of students, which is 8.  so 80/8 is 10.  My mean, or average, is 10.

MEDIAN
The median is the middle value of a data set in ranked order. If there is an odd number of
pieces of data, the median is the middle value in ranked order. If there is an even number of pieces of data, the median is the numerical average of the two middle values.  
Ex. Lets use the same numbers for the Age of my students, but remember to place them in least to least to greatest order.  5,7,8,9,11,12,13,15  If we have 8 students, then the number in the middle is actually two numbers 9 and 11.  What we would have to do is add the 9 and 11 for a total of 20 and divide the 20 by 2.  The median is 10.  If I had an odd number of ages, then the number in the middle would be the median.  5,7,8,9,     11,     12,13,15,16  the number 11 is directly in the middle with the same amount of numbers on each side.
 
MODE
The mode is the piece of data that occurs most frequently. If no value occurs more often than
any other, there is no mode. If there is more than one value that occurs most often, all these most-frequently-occurring values are modes. When there are exactly two modes, the data set is bimodal.

Ex. For 2, 3, 4, 5, 5, 6, 7, 8, 8, 8, 9, 11, the mode is 8.  For 2, 3, 4, 5, 5, 5, 7, 8, 8, 8, 9, 11, the modes are 5 and 8 (bimodal) which means that there are two modes this group of numbers. For 2, 3, 4, 5, 6, 7, 8, 9, 11, 13, 17, there is no mode.