Re: MU referencing
Hi Brendan,
I think the version that you presented does not follow the rules.
I would try this:
MU_1=THETA(1)
MU_2=0
Param1 = EXP(MU_1+ETA(1))
Param2 = EXP(MU_2+ETA(2))
Param = Param1*Param2**G2
where G2 = 0 (population 1) or 1 (population 2)
This is another (equivalent) option:
MU_1=THETA(1)
Param1 = EXP(MU_1+ETA(1))
Param = Param1*EXP(ETA(2)*G2)
I would also try correlated ETA(1) and ETA(2), and I wonder whether they will be estimated as collinear.
Leonid
--------------------------------------
Leonid Gibiansky, Ph.D.
President, QuantPharm LLC
web: www.quantpharm.com
e-mail: LGibiansky at quantpharm.com
tel: (301) 767 5566
Quoted reply history
On 5/26/2013 3:54 PM, Brendan Johnson wrote:
> Hi all,
>
> When using MU referencing, how do I code the situation where the typical
> value appears to be the same between two groups, but one group is more
> variable – how do I give these two groups different ETAs but essentially
> the same THETA?
>
> Is this legit?
>
> tvParam=THETA(.)
>
> MU_1=tvParam
>
> MU_2=tvParam
>
> Param1=MU_1+ETA(1)
>
> Param2=MU_2+ETA(2)
>
> Param=Param1*G1+Param2*G2
>
> Where G1 and G2 equal 0 or 1 based on which group the subject belongs.
>
> Thanks for the advice,
>
> Brendan