varians2.R

simpan=read.csv("C:/Tugas Statistika/varians2.csv", sep=";")
simpan

##    Nilai Kelas
## 1     30     1
## 2     40     1
## 3     50     1
## 4     60     1
## 5     70     1
## 6     80     1
## 7     90     1
## 8     10     2
## 9     20     2
## 10    30     2
## 11    40     2
## 12    50     2
## 13    60     2
## 14    70     2

library(doBy)
summaryBy(Nilai ~ Kelas, data = simpan, FUN= function(x)
{c(ratarata = mean(x), varians = var(x), jumlah=sum(x))})

##   Kelas Nilai.ratarata Nilai.varians Nilai.jumlah
## 1     1             60      466.6667          420
## 2     2             40      466.6667          280