1 개념

2 예제1

3 예제2

4 예제3

m1 <- 20
m2 <- 24
sd1 <- 5
sd2 <- 4
n1 <- 20
n2 <- 30
d <- abs((m1 - m2) / sqrt(((n1-1) * sd1^ 2 + (n2-1) * sd2^2) / (n1 + n2 - 2)))
d

> d
[1] 0.9043735

m1 <- 20
m2 <- 24
sd1 <- 5
sd2 <- 4
d <- abs((m1 - m2) / sqrt((sd1^2 + sd2^2) / 2))
d

> d
[1] 0.8834522

experimental_group <- rnorm(100, mean=100, sd=10)
control_group <- rnorm(110, mean=90, sd=20)

t.test(experimental_group, control_group)

effect_size <- (mean(experimental_group) - mean(control_group)) / sd(control_group)
effect_size

> t.test(experimental_group, control_group)

	Welch Two Sample t-test

data:  experimental_group and control_group
t = 5.9206, df = 162.36, p-value = 1.853e-08
alternative hypothesis: true difference in means is not equal to 0
95 percent confidence interval:
  8.060181 16.127373
sample estimates:
mean of x mean of y 
100.49207  88.39829 

> 
> effect_size <- (mean(experimental_group) - mean(control_group)) / sd(control_group)
> effect_size
[1] 0.6355913

• 0.0 ~ 0.2: small
  
• 0.3 ~ 0.5: medium
  
• 0.6 ~ 0.8: large