I fittted a LMM using the Standard Least Square platform, then attributed random effects. This is an example of an actual by predicted plot generated, I was wondering what the blue line represents
The Actual by Predicted Plot in Fit Least Squares platform is actually a leverage plot for the whole model. The blue line visualizes the regression null hypothesis that all parameters are zero (except the intercept) and the red line represents the alternative hypothesis that not all parameters are zero.