Median

The median is the center value in an ordered list of values; it's the middle.  You can find the median by finding the middle case.  The middle case of any ordered list will always be at rank

For example, if I have a sample of five student papers with word lengths of 329, 315, 349, 337 and 618, the middle paper will be the (5 + 1)/2 = 3rd in an ordered list.  First I put the five papers in order from least number of words to most.

I then find the case that is in the third rank.

The third case is 337.  This is the median.  Do not confuse the median rank (third) with the median (337).

As you can see, the median is not affected by the one student essay that is much longer than the others.  The median is resistant to outliers like this.

SPSS instructions for finding the median

SPSS instructions for comparing medians of different groups