Statistics and Probability Dictionary
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Quartiles divide a rank-ordered data set into
four equal parts. The values that divide each part are called
the first, second, and third quartiles; and they are denoted by
Q1, Q2, and Q3, respectively.
Note the relationship between quartiles and
Q1 corresponds to P25,
Q2 corresponds to P50,
Q3 corresponds to P75. Q2
median value in the set.