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I just wanted to make sure I'm interpreting my lme output correctly. I've set up a null model because I was told I could find the within-persons SD this way (Nelzek, 2012 MLM chapter). But the chapter is written in formulas, not in R code.

Here's the model I used. SubjectID is the grouping variable for person. 

nullmodel <- lme(dv1 ~ 1, data=dataset, random = ~1|subjectID,  na.action=na.exclude, method = "ML")
summary(nullmodel)

And here's the output summary. I assume the within-person SD for the dependent variable (dv1) is the intercept StdDev, but just wanted to check. Or if I'm interpreting this wrong let me know :)

Linear mixed-effects model fit by maximum likelihood
Data: dataset 
AIC      BIC    logLik
34404.33 34423.05 -17199.16

Random effects:
Formula: ~1 | subjectID
          (Intercept) Residual
StdDev:    13.39356   21.844

Fixed effects: dv1 ~ 1 
               Value Std.Error   DF  t-value p-value
(Intercept) 37.54255  1.336242 3677 28.09562       0

Standardized Within-Group Residuals:
       Min         Q1        Med         Q3        Max 
-2.7019919 -0.6909552 -0.1045376  0.6288470  3.4520256
alessothegreat
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  • The intercept StdDev for the random effect is the among subject standard deviation. I suppose the within individual standard deviation would be the residual standard deviation. – Axeman Sep 24 '19 at 18:02
  • Ah, good point. I'd love if someone could confirm as I'm trying to respond to an editor's request to calculate these for several variables. But that was helpful. – alessothegreat Sep 24 '19 at 18:18
  • You might have better luck on stats.stackexchange.com. – Axeman Sep 24 '19 at 18:28
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    Just wanted to report back and say that this was confirmed! Thanks for your help and suggestion Axeman. The standard deviation for the random intercepts that equals 13.39356 quantifies the variability between subjects. The residuals standard deviation (also known as the residual standard error) that equals 21.844 quantifies the variability of the outcome within a subject. – alessothegreat Sep 26 '19 at 19:41

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