The box chart shows the total distance (maximum-minimum) and.

Quartile spacing (dividing the array into minimum point, upper quartile, middle point, lower quartile and maximum point) is the quartile spacing between every two.

Advantages: Intuitive, each group of line segments contains 25% data, so the length of line segments actually reflects the density of data.

If you randomly input a set of more than 30 data and make a block diagram, you will find that the box will not always be uniform.

Disadvantages: sample size is not considered.

Variance and standard deviation are the same thing, but the units of standard deviation and mean are the same, so people tend to use standard deviation.

The standard deviation considers the sample size and dispersion, and gives the degree of variation.

Advantages: similar to the comprehensive index, it generally tells you the degree of variation in combination with the sample size. Suitable for preliminary screening.

Disadvantages: two groups of numbers with the same variance can differ by 108 thousand Li, and you must draw a box chart to understand the details