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percentile

(NL: percentiel)

A percentile of an ordered series of observations is one of basically 99 points that divides the series into 100 equally sized parts. The \(k\)th percentile, then, is a number where \(k\)% of the observations are smaller and \((100-k)\)% are greater than that number.

quartile

The quartiles are formed from five specific percentiles that divide the series into 4 equally sized parts:

  • \(\min\), the minimum, or percentile 0
  • \(Q_1\), the first quartile or percentile 25
  • \(Q_2\), the median, or percentile 50
  • \(Q_3\), the third quartile or percentile 75
  • \(\max\), the maximum, or percentile 100

The difference between the largest and smallest value is called range, and between the third and first quartiles is called interquartile range.