#menghitung standar deviasi
x <-c(70,75,80,80,90)
x
## [1] 70 75 80 80 90
length (x)
## [1] 5
table (x)
## x
## 70 75 80 90
## 1 1 2 1
table (x)/length (x)
## x
## 70 75 80 90
## 0.2 0.2 0.4 0.2
mean (x)
## [1] 79
#standar deviasi distribusi rata rata sampling
sd(x)
## [1] 7.416198
sd(x)*sqrt((length(x)-1)/length(x))
## [1] 6.63325
#kombinasi
sampel = combn (x,3)
sampel
## [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
## [1,] 70 70 70 70 70 70 75 75 75 80
## [2,] 75 75 75 80 80 80 80 80 80 80
## [3,] 80 80 90 80 90 90 80 90 90 90
#Mencari rata rata dari kombinasi yang dihasilkan
ratarata = colMeans(sampel)
ratarata
## [1] 75.00000 75.00000 78.33333 76.66667 80.00000 80.00000 78.33333 81.66667
## [9] 81.66667 83.33333
#mengubah format data
ratarata<-format(ratarata, digits = 4)
ratarata
## [1] "75.00" "75.00" "78.33" "76.67" "80.00" "80.00" "78.33" "81.67" "81.67"
## [10] "83.33"
#Mencari probabilitas data dan membuat plot
table (ratarata)
## ratarata
## 75.00 76.67 78.33 80.00 81.67 83.33
## 2 1 2 2 2 1
prob = table(ratarata)/length(ratarata)
prob
## ratarata
## 75.00 76.67 78.33 80.00 81.67 83.33
## 0.2 0.1 0.2 0.2 0.2 0.1
barplot(prob)
#Rata rata dari distribusi rata rata sampling
ratarata<- as.numeric(ratarata)
mean(ratarata)
## [1] 79
mean(x)
## [1] 79
#Standar deviasi rata rata
sd(ratarata)*sqrt((length(ratarata)-1)/length(ratarata))
## [1] 2.708014