BAB 7: UJI KESAMAAN VARIANS POPULASI

Menentukan Nilai Kritis F dengan R

qf(.95, df1 = 2, df2 = 15)

## [1] 3.68232

Penyelesaian dalam R untuk Uji Kesamaan Varians Populasi dengan Uji Levene

varians = read.csv("varians.csv")
varians

##    Nilai Kelas
## 1     70     1
## 2     80     1
## 3     87     1
## 4     77     1
## 5     80     1
## 6     80     2
## 7     85     2
## 8     70     2
## 9     77     2
## 10    85     2
## 11    60     2
## 12    80     2
## 13    70     3
## 14    87     3
## 15    90     3
## 16    77     3
## 17    76     3
## 18    87     3

library(car) 
leveneTest(varians$Nilai, varians$Kelas)

## Levene's Test for Homogeneity of Variance (center = median)
##       Df F value Pr(>F)
## group  2  0.4267 0.6604
##       15

#library(Rcmdr) 
#leveneTest(varians$Nilai, varians$Kelas)

library(lawstat) 
data(varians)
levene.test(varians[, "Nilai"], varians[, "Kelas"], location="median", correction.method="zero.correction") #Sesuai dengan Minitab

## 
##  Modified robust Brown-Forsythe Levene-type test based on the absolute
##  deviations from the median with modified structural zero removal method
##  and correction factor
## 
## data:  varians[, "Nilai"]
## Test Statistic = 0.4372, p-value = 0.6557

levene.test(varians[, "Nilai"], varians[, "Kelas"], location="mean", correction.method="zero.correction") #Sesuai dengan SPSS

## 
##  Classical Levene's test based on the absolute deviations from the mean
##  ( zero.correction not applied because the location is not set to median
##  )
## 
## data:  varians[, "Nilai"]
## Test Statistic = 0.64903, p-value = 0.5366

Contoh Kasus 2, Uji Kesamaan Varians Populasi dengan Uji Levene (Contoh Perhitungan dan Penyelesaian dengan R)

simpan = read.csv("varians2.csv") #membaca data varians.csv
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

simpan = read.csv("varians2.csv") #membaca data varians.csv
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(lawstat)
data(simpan)
levene.test(simpan[, "Nilai"], simpan[, "Kelas"], location = "mean", correction.method = "zero.correction")

## 
##  Classical Levene's test based on the absolute deviations from the mean
##  ( zero.correction not applied because the location is not set to median
##  )
## 
## data:  simpan[, "Nilai"]
## Test Statistic = 1.4336e-32, p-value = 1