The upper quartile, for a set of ordinal observations, is a value such that a quarter of the observations have a greater value. Similarly, the lower quartile is a value such that
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Quartiles are like 'medians' First get the median, then get the median of the lower half which is the lower quartile. Do the same for the upper half. Source(s) Wikipedia.
http://answers.yahoo.com/question/index?qid=200907...

For Lower Quartile: Sort all observations in ascending order Comput...
http://www.chacha.com/question/howdoyoufindthe...

use the chi square test
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