  The exact nature of the QCD phase transition has still not been determined
conclusively, and there are contradictory results from lattice QCD simulations
about the scaling behavior for two quark flavors. Ultimately, this issue can be
resolved only by a careful scaling and finite-size scaling analysis of the
lattice results. We use a renormalization group approach to obtain finite-size
scaling functions for the O(4)-model, which are relevant for this analysis. Our
results are applicable to Lattice QCD studies of the QCD phase boundary.
