Thus far, we have introduced and applied the conventional battery of statistical methods and approaches to meta-regression analysis. The purpose of this chapter is to delve a bit deeper into the statistical foundation of MRA. This book is intended to be a practical guide for researchers who wish to conduct meta-analyses in economics and business; thus, we have avoided non-essential mathematics and associated technicalities. In this chapter, we present: a theory of MRA directly derived from econometric and statistical theory; a more mathematical and detailed representation of the typical MRA models needed for economic and business applications; a more careful derivation of our MRA models of publication selection; and further technical details about the use of panel (or multilevel) methods in meta-analysis. In the process, we will show how MRA results are entirely unaffected by issues of observed and unobservable study quality when properly modeled. Applied researchers may wish to skim the cream of this chapter.