I have a variable measured four times age 14, 16, 18 and 20 I have done a series of GCM to find the best one. in particular the first model tested was a no-growth model (only intercept) The second was a linear model. In this model we fixed the factor loadings on the slope at 0, 1, 2, 3. The third model examined a non-linear growth. The chi square difference test revealed that the best model is the non linear one. yt = n0 + n1 xt + et ; with x3 and x4 as parameters to be estimated;
Now a referee told me that it is crucial that the authors evaluate the following submodel: yt = n1 xt + et, with x2, x3, and x4 as parameters to be estimated and x1 =1.
this is the input i have wrote: s by MD14@1 MD16*1 MD18*2 MD20*3; md16 with md18 (4); md14 with md16 (2); md18 with md20 (2); MD14 (8); MD18 (10); model female:
md16 with md18 (5); md14 with md16 (1); md18 with md20 (1); MD14 (8); MD18 (10);
Is this model nested with the linear one? and is the requested model make sense? Thank you
thank you , this model is identified with a good fit. The reviewer cited the work of Meredith and Tisak (1990). My problem is that I don't think it is nested with the other models i tested. Is it right?
Even if the model is nested, with an implied zero variance of the intercept growth factor, difference testing cannot be used because a variance of zero in on the border of the admissible parameter space.