How can I interpret this plot in the output of SimBiology?

I constructed the compartment model, fitted the data and got the output but one of the output that I am not clearly understand is the plot between predicted concentration and observed concentration that I want to know how I can interpret this plot. And what is the Y-axis?

Answer 1

[Arthur Goldsipe]

This is normplot of the residuals. You can read more about normplot here, but the basic idea is that this plot is used to tell you whether your residuals are normally distributed. The point on the lower left and the point on the upper right represent outlier residuals for data points that are not well described by your model.