I tried to use a linear model to explain a variable "age" with two variables "x1" and "x2".
I can clearly see a decreasing slope inside my scatterplot for age vs x1, or age vs x2, and the pvalue of each coefficient of my model is <0.001, but there is too much dispersion (R2 of my linear model is < 0.5).
I don't have much information, so i would like to add a "prior" information, the "exact distribution" of "age" inside a population, using the population censing of my country (which then does not depend on "x1" or "x2" ...). Hope this helps to narrow down the error. I'm not sure if I can do that, and if yes, how ?
I'm sure the linear model is a suitable model to explain the relationship between age and x1 and x2, but it cannot make precise predictions.