In the print() output of a multi-level model

```
stan_glmer
family: gaussian [identity]
formula: ec ~ g + (g | chr)
observations: 608
------
Median MAD_SD
(Intercept) 51.434 0.777
gv 3.136 0.813
Auxiliary parameter(s):
Median MAD_SD
sigma 5.499 0.159
Error terms:
Groups Name Std.Dev. Corr
chr (Intercept) 1.772
gv 1.746 -0.34
Residual 5.503
Num. levels: chr 5
```

I have the \sigma^2_y of 5.503 as the Residuals and the \sigma^2_\alpha and \sigma^2_\beta, all given under *Error terms*. This *sigma* though is slightly different here, 5.499 but in some other models it is the same, to at least the third or fourth decimal.

In this tutorial the difference between residuals en sigma is not explained.

Could somebody explain the difference between the two?