it is the top 25% of the data.
http://wiki.answers.com/Q/What_is_the_definition_f...

1. Add 1 to the number of items in your data set. For example, if your data set has 23 items, add 1 to 23 to get 24. 2. Multiply the result by 3/4 to find the item in your data set
http://www.ehow.com/how_8359496_upperquartile.htm...

The third quartile (designated Q3) = upper quartile = cuts off highest 25% of data, or
http://www.chacha.com/question/whatisanupperqu...

It's easy to find out: just plug in the sequence 1, 2, 3, 4, 5 and ask for the statistics. The first quartile comes back as 1.75. Therefore, it's picking a point between 1 and 2
http://www.quora.com/Whatdefinitionofquartiled...
