Code:

```
library(lme4)
fm1 <- lmer(Reaction ~ Days + (Days | Subject), sleepstudy)
```

Can you please explain me the result of the following commands ?

Code:

```
attr(summary(fm1)$varcor$Subject,"stddev")
(Intercept) Days
24.740448 5.922133
c(sd(ranef(fm1)$Subject[,1]),sd(ranef(fm1)$Subject[,2]))
[1] 21.595943 5.455217
summary(fm1)$sigma
[1] 25.59182
residuals(summary(fm1))
sd(residuals(summary(fm1)))
[1] 0.9183965
```

That is , if one asks me what is the meaning of the results that you have found from "sd(ranef(fm1)$Subject[,1])" and "attr(summary(fm1)$varcor$Subject,"stddev")[1]" ? Both are standard deviation of "Intercept" but of course there is difference between these two results . But I don't know what is this ?

In "?getMe" , it is said that from "summary(fm1)$sigma" , we found residual standard error . But why doesn't the result match with "sd(residuals(summary(fm1)))" ?

Also , In "summary(fm1)$varcor" there is value 0.066 under the column "Corr" . Does it mean correlation between two random effects "(Intercept)" and "Days " is 0.066 ?

Any help is appreciated . Thank you .