a better example: drinking coffee *causes* alertness during exam period. bottled water does not affect alertness.
.'. the true life equation is: alertness=coffee but say we forget to measure coffee in our model but feel exploratative, the fictional model is: alertness=bottled water+body weight+age I assume that the only way to know the validity of the coeffiients (and their direction!) is to look at how much of the ultimate variable is predicted. [this seems unreliable given small overall predictive power of regression models seen in exploratory research - ex. does egg consumption correlate with serum cholesterol?] . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
