  Cosmic Microwave Background (CMB) anisotropies that result from quantum
fluctuations during inflation are explored and the impact of their ``cosmic
variance'' on the ability to use existing data to probe inflationary models is
studied. We calculate the rms temperature fluctuation, and its cosmic variance,
for a number of experiments and for models with primordial power spectra which
range from $n={1\over 2}$ to $1$. We find: (1) cosmic variance obscures the
information which can be extracted, so a comparison of the rms temperature
fluctuation on small scales with the COBE result can fix $n$ to only
$\approx\pm 0.2$ at best; (2) measurements of the rms fluctuation on
$1^{\circ}$ scales may not allow one to unambiguously infer the tensor
contribution to the COBE anisotropy; (3) comparison of this contribution with
the predictions of inflation are ambiguous if the quadrupole anisotropy alone
is utilized. We discuss means for minimizing the uncertainty due to cosmic
variance in comparisons between experiments.
