  The determination of low-energy constants from data is an important component
of most effective field theory programs, including that of chiral perturbation
theory. We propose a novel method based on Bayesian probability theory which
allows us to address several shortcomings of the standard approach to parameter
extraction. Using a toy-model we argue that the Bayesian approach is ideally
suited for the application in effective field theories. We also discuss the
application to lattice QCD data.
