Quartile
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In descriptive statistics, a quartile is any of the three values which divide the sorted data set into four equal parts, so that each part represents 1/4th of the sample or population.
Thus:
- first quartile (designated Q1) = lower quartile = cuts off lowest 25% of data = 25th percentile
- second quartile (designated Q2) = median = cuts data set in half = 50th percentile
- third quartile (designated Q3) = upper quartile = cuts off highest 25% of data, or lowest 75% = 75th percentile
The difference between the upper and lower quartiles is called the interquartile range.
Example 1:
Data Set: 6, 47, 49, 15, 42, 41, 7, 39, 43, 40, 36
Ordered Data Set: 6, 7, 15, 36, 39, 40, 41, 42, 43, 47, 49
Q1 = 15
Q2 = 40
Q3 = 43
Example 2:
Ordered Data Set: 7, 15, 36, 39, 40, 41
Q1 = 15
Q2 = (39+36)/2 = 37.5
Q3 = 40
[edit] Calculating quartiles
See Quantile for methods. The quartile is calculated as the 4-quantile.
[edit] See also
[edit] External links
- Quartiles-From MathForum.org
- Quartiles - an example how to calculate it
- Free Online Software (Calculator) computes Quartiles for any data set according to 8 different definitions.
