> a1 <- function() sum((runif(100)+1)*(runif(100)+1))/100
> x1 <- vector(); for (i in 1:1000) x1 <<- c(x1,a1())
> sd(x1)
[1] 0.06115756
> a2 <- function() (sum(runif(100)+1)/100)*(sum(runif(100)+1)/100)
> x2 <- vector(); for (i in 1:1000) x2 <<- c(x2,a2())
> sd(x2)
[1] 0.06233367

A1の方がよさげだな