Calculating and extracting variance

You are assuming that the variation around the intercept is randomly influenced by site, and the degree to which it is influenced is normally distributed with a variance of d. Use two different methods to find the estimate of variance, first by calculating it manually, and then by extracting it using VarCorr().

The output of random_int_model is:

Linear mixed-effects model fit by REML
  Data: orchids 
  Log-restricted-likelihood: -420.2667
  Fixed: abundance ~ humidity 
(Intercept)    humidity 
 -4.3751595   0.1785742 

Random effects:
 Formula: ~1 | site
        (Intercept) Residual
StdDev:    3.515514 3.066667

Number of Observations: 160
Number of Groups: 8

Note that the orchids data set, random_int_model model, and nlme library have been preloaded.

Calculate the estimate of variance for the random intercept of random_int_model by examining values in the model output.
Extract the estimate of variance using VarCorr().

Exercise

Calculating and extracting variance

Instructions