[R-sig-ME] When a higher level can't be modeled due to one row

[Farzad Keyhan]

Dear Colleagues,

I initially posted my query on the meta-analysis SIG. But I realized
my question is related to multilevel modeling.

Below is my data structure. If in row # 3, "measure" was 2 (instead of
1), then, I could model "measure" as a level above "study":

 (1 | measure / study / outcome)

But right now, because in study 2 (rows # 3 and 4) "measure" can vary,
"measure" can't be considered a level above "study".

On the other hand, because "measure" varies only in one "study" level
(i.e., study 2), I can't model "measure" as a crossed effect with
"study" either:

 (1 | study / outcome) + (1 | measure)

So, to model "measure" as a random factor what can we do?

Best,
Fred
   measure  study  outcome
   1              1          1
   1              1          2
# 1              2          1<--row #3
   2              2          1
   1              3          3
   1              3          2
   2              4          3
   9              5          1
   9              6          2