  We discuss the effects of finite sky coverage and the uncertainty in
extracting information about the power spectrum from experiments on small
angular scales. In general the cosmic variance is enhanced by a factor of
$4\pi/A$, where $A$ is the solid angle sampled by the experiment. As a rough
guide, an experiment with sensitivity peaking at the $\ell$th multipole has to
cover $\simgt\ell$ independent patches to have a lower ``sample variance'' than
for a whole-sky measurement of the quadrupole. Our approach gives a relatively
simple way of attaching an error bar to the theoretical prediction for a
particular experiment, and thereby comparing theories with experimental
results, without the need for computationally-intensive Maximum Likelihood or
Monte Carlo calculations.
