x = round(rnorm(10^6,4,1)); x[x<1]=1; x[x>7]= 7; table(x)
x
     1      2      3      4      5      6      7
  6189  60309 241098 383199 242159  60808   6238
sd(x)
## 1.039021   # reasonably close to 1
mean(x)
## 4.002206   # reasonably close to 4

s = replicate( 10^6, sum(rnorm(4, 4, 1)) )
mean(s > 13.5 & s < 18.5)
## 0.788404