I have a study design question I was having trouble with.
I have 2 groups (placebo & case) and 3 timepoints.
I could use 1 2-way Repeated Measures ANOVA to analyse the data, but
the timepoints would (surely) simply be treated as 3 groups, rather
than 3 ordinal points.
Is there a method that will do this for me?
(And if there isn't, how would I interpret a result that went up and
then back down again when I'm expecting a dose response?)

Thanks Bruce,

To be honest, I'm hoping for a linear trend in this study. A quadratic
one wouldn't make much sense in this case, and with only 3 time points
wouldn't be very convincing either. But I do have another study (not
repeated measures, 5 ordinal groups and one continuous variable) where
it looks like there might be quadratic trend (confession here to
peeking at the data halfway through). It might be very useful for that
one, thanks!

On Mar 14, 4:30 am, greg <jsg...@lycos.co.uk> wrote:

Thanks Bruce,

To be honest, I'm hoping for a linear trend in this study. A quadratic
one wouldn't make much sense in this case, and with only 3 time points
wouldn't be very convincing either. But I do have another study (not
repeated measures, 5 ordinal groups and one continuous variable) where
it looks like there might be quadratic trend (confession here to
peeking at the data halfway through). It might be very useful for that
one, thanks!

I just re-read your first post.  I guess "expecting" was the wrong
word.  It sounds like you *observed* a quadratic trend (result went
up, then back down).

--
Bruce Weaver
bwea...@lakeheadu.cawww.angelfire.com/wv/bwhomedir
"When all else fails, RTFM."

On Mar 14, 1:28 pm, Bruce Weaver <bwea...@lakeheadu.ca> wrote:
On Mar 14, 4:30 am, greg <jsg...@lycos.co.uk> wrote:

Thanks Bruce,
To be honest, I'm hoping for a linear trend in this study. A quadratic
one wouldn't make much sense in this case, and with only 3 time points
wouldn't be very convincing either. But I do have another study (not
repeated measures, 5 ordinal groups and one continuous variable) where
it looks like there might be quadratic trend (confession here to
peeking at the data halfway through). It might be very useful for that
one, thanks!
I just re-read your first post. I guess "expecting" was the wrong
word. It sounds like you *observed* a quadratic trend (result went
up, then back down).

--
Bruce Weaver
bwea...@lakeheadu.cawww.angelfire.com/wv/bwhomedir
"When all else fails, RTFM."

It looks like there may be a slight, weakly 'significant' unexpected
up-down pattern in one variable. In an ideal world, I'd like a method
that would take into account the fact that the groups are ordinal (in
terms of time sequence) and I'm sure there are better methods out
there.

I'd be happy to say that there was a quadratic relationship if I was
convinced there really was one, but I was concerned that by treating
the time points as different groups, the ANOVA may be giving me a
false positive.