Posted by
Maguin, Eugene on
URL: http://spssx-discussion.165.s1.nabble.com/Temporal-stability-using-multilevel-modeling-tp5736274p5736288.html
Ignoring the number of observations per person, I visualize you wanting to run a two level logistic regression model in which the only level 1 predicto, other than the intercept, is the prior observation. And, you'd like to have both a random intercept and a random slope, which I construe to be your AR(1) term, because you want to relate variation in the level 1 slope to person characteristics. In reality, I don't think you can get that equation to solve with only six observations and a random slope. I think you could get an intercept only model to solve but's not quite what you want. So, what if you tabulated the number of reversals in the observation string. Example: (101) has two reversals; (100) as one. The drawback is that (010) and (101) have the same number of reversals so perhaps another variable to use is the initial value.
Perhaps people that have worked with data like this have better suggestions/methods.
Gene Maguin
-----Original Message-----
From: SPSSX(r) Discussion <
[hidden email]> On Behalf Of Oliver
Sent: Saturday, June 23, 2018 9:23 AM
To:
[hidden email]
Subject: Temporal stability using multilevel modeling
Hi everyone,
I'm interested in examining the temporal stability of a behavior that was measured at 6 different time points (i.e., once a month for 6 consecutive months). My sample includes 100 patients, and most of them have data on the
6 time points. I have three questions:
1) For the whole sample, would it be possible to use AR1 as a measure of temporal stability of the behavior ? Given that AR1 has often been described as a measure of "temporal dependency", this seems to make sense. It is important to note, however, that there are minor between-person variations in time intervals in-between each of the assessment time points, which is typical in clinical research. Perhaps AR1 requires a pure "time-series"
design with equally spaced intervals in between assessments ?
2) My behavior of interest is a binary variable (i.e., presence/absence). I tried to get the AR1 using the GLMM procedure in SPSS, and the AR1 is not generated. Is it possible to get AR1 with a binary outcome ? If so, is there any syntax specification needed ? If not, is there an alternative to AR1 with a binary outcome ?
3) The second goal of my study is to examine the within-person (i.e., Level
1) predictors of behavior stability. Therefore, I was wondering whether it would be possible to derive a within-person indicator (e.g., AR1) of behavior stability ? If so, I could use this indicator as an outcome measure, which could then be predicted by other within-person (i.e., Level
1) variables.
Thanks in advance to all of you for your help.
Oliver
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