Modifying the first example in help('lme', pac='nlme'):
library(nlme)
fm1 <- lme(distance ~ age, data = Orthodont) # random is ~ age
fm1$sigma
fm1.2 <- lme(2*distance ~ age, data = Orthodont) # random is ~ age
fm1.2$sigma
Conclusion: Standard deviation, as indicated in help('lmeObject').
Hope this helps.
Spencer Graves
On 12/18/21 4:00 AM, Eric Berger wrote:
You can run a test. Multiply all your data by a scalar, say 2.
If this changes the result lme_mod$sigma by a factor of 2, then it is
a std deviation.
If it changes the result by a factor of 4, then it is a variance.
HTH,
Eric
On Sat, Dec 18, 2021 at 11:26 AM Courtney Van Den elzen
<courtney.vandenel...@colorado.edu> wrote:
Hi R-help,
I am a researcher fitting linear mixed models using the package nlme. I am
wondering whether the sigma value that is outputted as part of the model
object is standard deviation or variance? for example, I might fit a model
lme_mod <- nlme::lme(response ~ predictor1 + predictor2, random =
(~1|grouping1))
I am wondering whether lme_mod$sigma is actually a standard deviation or if
it's a variance.
Thanks so much,
Courtney
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