Quartile

Quartile

Video: CALCULATE QUARTILES

A quartile is a type of quantile. The first quartile (Q1) is defined as the middle number between the smallest number and the median of the data set. The second quartile (Q2) is the median of the data. The third quartile (Q3) is the middle value between the median and the highest value of the data set.

In applications of statistics such as epidemiology, sociology and finance, the quartiles of a ranked set of data values are the four subsets whose boundaries are the three quartile points. Thus an individual item might be described as being "in the upper quartile".

Definitions

Boxplot (with quartiles and an interquartile range) and a probability density function (pdf) of a normal N(0,1σ2) population

Symbol
Names
Definition
Q1
  • first quartile
  • lower quartile
  • 25th percentile
splits off the lowest 25% of data from the highest 75%
Q2
  • second quartile
  • median
  • 50th percentile
cuts data set in half
Q3
  • third quartile
  • upper quartile
  • 75th percentile
splits off the highest 25% of data from the lowest 75%
Computing methods

For discrete distributions, there is no universal agreement on selecting the quartile values.[1]

Method 1

  1. Use the median to divide the ordered data set .....

 

 

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