Medicare's Prospective Payment System pays U.S. teaching hospitals for
the indirect costs of medical education based on a regression coeffic
ient in a cost function. In regression studies using health care data,
it is common for explanatory variables to be measured imperfectly, ye
t the potential for measurement error is often ignored. In this paper,
U.S. Department of Veterans Affairs data is used to examine issues of
health care production estimation and the use of regression estimates
like the teaching adjustment factor. The findings show that measureme
nt error and persistent multicollinearity confound attempts to have a
large degree of confidence in the precise magnitude of parameter estim
ates.