R help - Dec 2021 - nlme::lme sigma parameter standard deviation or variance?

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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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.VanDenelzen at 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
>
>         [[alternative HTML version deleted]]
>
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