To date, the strongest indication of charge symmetry violation in parton
distributions has been obtained by comparing the F2 structure functions from
CCFR neutrino data and NMC muon data. We show that in order to make precise
tests of charge symmetry with the neutrino data, two conditions must be
satisfied. First, the nuclear shadowing calculations must be made explicitly
for neutrinos, not simply taken from muon data on nuclei. Second, the
contribution of strange and charm quarks should be calculated explicitly using
next-to-leading order [NLO] QCD, and the ``slow rescaling'' charm threshold
correction should not be applied to the neutrino data. When these criteria are
satisfied, the comparison is consistent with charge symmetry within the
experimental errors and the present uncertainty in the strange quark
distribution of the nucleon.Comment: 18 pages, 4 figure
