Re: Temporal stability using multilevel modeling

Posted by Rich Ulrich on
URL: http://spssx-discussion.165.s1.nabble.com/Temporal-stability-using-multilevel-modeling-tp5736274p5736276.html

Like Andy, I'm not speaking to the SPSS questions, either, and I think

AR1 won't be useful. Here are other reasons.  Dichotomous measures

need more cases to match the power achieved by continuous measures.

Six points is an awfully small time series for continuous data for using "time

series methods", I think.  No doubt there are exceptions. You do have 100

parallel series ... which isn't the standard TS problem. My practical experience

with Time series is zero, but, unfortunately for your prospect of getting a better

answer here, we've dealt with very few TS problems, and I suspect that we

have no experts here of that specialty.

The stock markets call their instability "lability" and they measure it from the

standard deviation or variance of stock prices. Variance of a dichotomy is computed

from its mean (i.e., proportion), so I suggest that you get a transparent and obvious

measure of stability/volatility by counting and reporting the number of changes

observed for each ID.   (By the way, if most of your scores for a subject are identical,

at zero or 1, you have a different problem of lack-of-usable-variance for analysis.)

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Rich Ulrich

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From: SPSSX(r) Discussion <[hidden email]> on behalf of Oliver <[hidden email]>
Sent: Saturday, June 23, 2018 9:22:42 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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