You do (n + 1) / 2
'n' being the total number of scores
then that number will give you the score number that is the median.
eq- theres 20 scores
so (20+2) / 2
= 10.5
therefore the median is the number between the 10th and the 11ths scores. I think you add a cumulative frequency column to the table then and work out which score it was.
Anyone tell me if im wrong.