mean, median, mode, standard deviation and range

Mean, median, and mode are three kinds of "averages".
The mean is the usual average. (算数平均)
The median is the middle value. (中间数)
The mode is the number that is repeated more often than any other. (众数)
ex.
13, 18, 13, 14, 13, 16, 14, 21, 13
mean=(13+18+13+14+13+16+14+21+13)/9=15

13, 18, 13, 14, 13, 16, 14, 21, 13⇒(sort)⇒13, 13, 13, 13, 14, 14, 16, 18, 21
median=14

13, 18, 13, 14, 13, 16, 14, 21, 13
mode=13

standard deviation (SD)：

The largest value in the list is 21, and the smallest is 13, so the range is 21 – 13 = 8.

> x=c(13, 18, 13, 14, 13, 16, 14, 21, 13)

> x

[1] 13 18 13 14 13 16 14 21 13

> mean(x)

[1] 15

> median(x)

[1] 14

> sd(x)

[1] 2.828427

> range(x)

[1] 13 21

※Rにはmode関数はない。
https://www.purplemath.com/modules/meanmode.htm