The first quartile (also called the lower quartile) is the number below which lies the 25 percent of the bottom data. The second quartile (the median) divides the range in the middle and has 50 percent of the data below it. The third quartile (also called the upper quartile) has 75 percent of the data below it and the top 25 percent of the data above it. See also interquartile range and percentile.
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