Let data set : 65 , 70 , 75 ,80 , 85 ; =75 , s =5
65 70 75 80 85
-2s - s +2s +s
z= -2 z= -1 z= 0 z= 1 z= 2
For data value 83:
Test marks are shown here. On which test she perform better?
Math marks: 65 50 45 ; =53.3 , s=10.4
Biology marks: 80 75 70 ; =75 , s=5
, the relative position in math class is higher than her the relative position in biology class. She performs better in math paper than biology paper.
(the marks that she get from biology paper is more than mathematics paper but we cannot compare the marks directly because the papers are different i.e. number of question, standard of questions and so on, that is why we have to compare the relative position)