We present a list of possible effective theories which may describe a QHE edge at filling fraction ν = 5/2. We show that there exist several abelian and non-abelian effective theories (apart from those discussed in the literature) compatible with the physical requirements imposed by the microscopic nature of the system. We compare predictions of these theories with previous proposals and with the results of recent experiments. We identify a set of theories, both abelian and non-abelian, that cannot be distinguished based on the quasihole tunneling data only. We discuss what experimental information may be useful in resolving the ambiguity.PACS numbers: 03.65.Yz, 85.35.Ds One of the most striking predictions of the theory of the fractional quantum Hall effect is that a twodimensional electron gas in a strong magnetic field may exhibit a ground state supporting excitations (quasiparticles) with non-abelian braid statistics. In particular, Wen [1] and Moore and Read [2] have brought forward arguments attempting to explain the ν = 5/2 conductance plateau as a manifestation of such a "nonabelian" state. Not only is this possibility fascinating from the theoretical point of view, it also holds promise for concrete implementations of topologically protected quantum algorithms [3].Among non-abelian quantum Hall states, perhaps the simplest is the Moore-Read (Pfaffian) state, which has a simple intuitive interpretation as a p-wave paired state of composite fermions. The intuitive appeal of the MooreRead state does, however, not give a compelling clue as to its microscopic justification. The Hamiltonian of the many-electron system in a strong magnetic field is not amenable to a well-controlled perturbative treatment, whether in the electron or in the composite-fermion basis. Exact diagonalization numerical studies do not allow one to make fully reliable statements about macroscopically large systems. In this situation the decisive word about the nature of the ν = 5/2 state must come from experiments. A natural target for experimental investigations is the edge of an incompressible quantum Hall fluid supporting gapless excitations, including electric currents, and fractionally charged quasi-holes.In a recent experiment [4], properties of the ν = 5/2 state were investigated by means of a transport measurement in a quantum Hall sample with a narrow constriction. The parameters of the constriction were tuned in such a way that it served as a weak link between two ν = 5/2 quantum Hall edges. The electrical conductance of the constriction exhibits a zero bias peak, whose scaling with temperature is consistent with the assumption that the current is due to weak tunneling of fractionally charged quasi-particles. By fitting the shape of the zero-bias conductance peak to the predictions of a model-independent theory [6] at five different temperatures the experimentalists produced a two-parameter confidence map for the electric charge e * and the scaling dimension, g, of the most relevant (in the renormalization group sense) qua...