  Very Long Baseline Interferometric (VLBI) observations of quasar jets enable
one to measure many theoretically expected effects. Estimating the significance
of observational findings is complicated by the correlated noise in the image
plane. A reliable and well justified approach to estimate the uncertainties of
VLBI results is needed as well as significance testing criteria. We propose to
use bootstrap for both tasks. Using simulations we find that bootstrap-based
errors for the full intensity, rotation measure, and spectral index maps have
coverage closer to the nominal values than conventionally obtained errors. The
proposed method naturally takes into account heterogeneous interferometric
arrays (such as Space VLBI) and can be easily extended to account for
instrumental calibration factors.
