[R-meta] Distinguishing between the design of longitudinal studies

[Stefanou Revesz]

Dear List Members,

We are meta-analyzing a number of longitudinal studies. But our
studies have three general research designs (below).

We are wondering, other than creating study-level moderators to
distinguish between the designs or how many treatments each study uses
etc., what *time-level* or *effect-size-level* moderators we should
control for in our meta-analysis?

First, we have studies that make an observation (o) prior to a
treatment (x), and then, make follow-up observation(s):

o x o o
o    o o   <-- control group

Second, we have studies that make an observation (o) prior to a
treatment (x), then, make follow-up observation on that treatment, but
then again introduce the treatment and make follow-up observation(s):

o x o x o  o
o    o    o  o  <-- control group

Third, we have studies that make an observation (o) prior to
successive treatments (x), and then, make follow-up observation(s) on
those treatments:

o x x x o  o
o         o  o  <-- control group

Thank you!
Stefanou