  To calculate the temperature at which a first-order cosmological phase
transition occurs, one must calculate $F_c(T)$, the free energy of a critical
bubble configuration. $F_c(T)$ is often approximated by the classical energy
plus an integral over the bubble of the effective potential; one must choose a
method for calculating the effective potential when $V''<0$. We test different
effective potential approximations at one loop. The agreement is best if one
pulls a factor of $\mu^4/T^4$ into the decay rate prefactor [where $\mu^2 =
V''(\phi_f)$], and takes the real part of the effective potential in the region
$V''<0$. We perform a similar analysis on the 1-dimensional kink.
