  As a superconductor goes from the normal state into the superconducting
state, the voltage vs. current characteristics at low currents change from
linear to non-linear. We show theoretically and experimentally that the
addition of current noise to non-linear voltage vs. current curves will create
ohmic behavior. Ohmic response at low currents for temperatures below the
critical temperature $T_c$ mimics the phase transition and leads to incorrect
values for $T_c$ and the critical exponents $\nu$ and $z$. The ohmic response
occurs at low currents, when the applied current $I_0$ is smaller than the
width of the probability distribution $\sigma_I$, and will occur in both the
zero-field transition and the vortex-glass transition. Our results indicate
that the transition temperature and critical exponents extracted from the
conventional scaling analysis are inaccurate if current noise is not filtered
out. This is a possible explanation for the wide range of critical exponents
found in the literature.
