Why population PK approach is good for pooling data compared to Classical statistical analysis?

From: Ayyappa.5.chaturvedula Date: October 16, 2008 technical Source: cognigen.com
Dear Group, Could anybody explain or direct me to some literature why population PK approach allows us to pool data from different studies but no classical statistical analysis? Regards, Ayyappa Chaturvedula GlaxoSmithKline 1500 Littleton Road, Parsippany, NJ 07054 Ph:9738892200