I have a large(2010X 4) data set and I need to calculate the effects of cycles and stresses on my wave speeds along with the interaction between them. My wavespeeds are collected for 4 stress levels so stresses here are repeated measurements. Here is a glimpse of what my stacked table looks like : N=subject on first row, CYC=cycle number on second row, STR: stress levels on third row and wave speeds collected in fourth row
I used the Mixed model on JMP pro where I have my cycle and stresses full factorial on fixed effects, N(subject number) on random effects, and wave speeds in Y.
My question here is in repeated structure, I am unsure whether I should use a residual structure or AR(1) for repeated covariance structure. when I use residual structure for my co variance these are my results :
In the fixed effects, the cycles, and stresses individually shows significance however cyc*stress interaction does not show significance which is not what is interpreted . and the cycles Nparm shows 43 which is taking account of only one fascic How do I approach this problem ?
