there are 4 types of data..
i) Live data - this is real data
ii) normal Data - this is data that may or may not be made up, but it is within the range of the criteria
iii) Extreme data - this is data that is still in the criteria but it is at the far ends of the range
iv) Abnormal data - this is data that is incorrect and doesn't fall within the criteria...
lets take the range of a value as >100 AND <=200
over here abnormal data would be examples like -1, 2, 3, 4, 201 202... on and on (100 is also an abnormal data bcuz the criteria is only MORE than hundred AND less than OR equal to 200)
extreme data would be 101,102, 200,199... normal data would probably come around 150...
hope that answers the question...
best of luck 2 u...