what is the difference between py and sigma_y what is the prior of a kristofferson model what is the prior to kristofferson's model what is the prior of $y_i what is the parameter for the sigma_y interval why is there a prior model for sigma_y what model has $y_i$ missing data what is the parameter y_i in the skew what is the model of drum beats what model is used to measure sigma y? why is the sigma_y parameter considered a nuisance parameter? why is the sigma_y parameter considered a nuisance parameter what is the kristofferson model what is the prior to sigma y what is the prior to a sigma_y? what is the underlying problem of the wings kristofferson model? why is the sigma_y parameter considered a nuisance parameter? what is the prior value for a sigma value why is $m_i$ a nuisance parameter? why is the prior of a sd parameter missing