Box Plot
Box plot (English: Box plot), also known as box and whisker plot, box plot, box plot or box plot, is a statistical plot used to display a set of scattered data. Named because of its shape like a box. It is also often used in various fields, commonly used in quality management, to quickly identify outliers.
The biggest advantage of the box chart is that it is not affected by outliers, can accurately and stably depict the discrete distribution of data, and it is also conducive to data cleaning.
If you want to understand the box plot, then you must understand...
Five for "number"
We set a number sequence as an example: 12,15,17,19,20,23,25,28,30,33,34,35,36,37 explain these five because of "several"
1. Lower quartile Q1
(1) Determine the position of the quartile. The location of Qi=i(n+1)/4, where i=1, 2, 3. n represents the number of items contained in the sequence.
(2) According to the position, calculate the corresponding quartile.
In the example:
The location of Q1=(14+1)/4=3.75,
Q1=0.25×third item+0.75×fourth item=0.25×17+0.75×19=18.5;
2. Median (second quartile) Q2
The median is the number in the middle of a group of numbers arranged from small to large. If the sequence number is an even number, the median of the group is the average of the middle two numbers.
In the example:
The location of Q2=2(14+1)/4=7.5,
Q2=0.5×seventh item+0.5×eighth item=0.5×25+0.5×28=26.5
3. Upper quartile Q3
The calculation method is the same as the lower quartile.
In the example:
The location of Q3=3(14+1)/4=11.25,
Q3=0.75×the eleventh item+0.25×the twelfth item=0.75×34+0.25×35=34.25.
4. Upper limit
The upper limit is the maximum value in the non-anomalous range.
The first thing to know is how to calculate the interquartile range?
Interquartile range IQR=Q3-Q1, then the upper limit=Q3+1.5IQR
5. Lower limit
The lower limit is the minimum value in the non-anomalous range.
Lower limit = Q1-1.5IQR