Where are you calling from? <a href=" http://loughcu.ie/beta-sitosterol-for-prostate-health.pptx ">beta sitosterol 600 mg</a> Now one of those omitted variables is almost certainly hospital performance, or quality, unless you think such things don’t matter at all .  But it is almost certain there are others as well (in addition, the model is almost certainly &#8220;misspecified&#8221; as well, which introduces additional complications and biases). But the bottom line is that hospital performance will only explain some of the &#8220;excess&#8221; deaths calculated from the model &#8211; and the model itself won&#8217;t tell us how much.