  Radio interferometric data are used to estimate the sky brightness
distributions in radio frequencies. Here we focus on estimators of the
large-scale structure and the power spectrum of the sky brightness distribution
inferred from radio interferometric observations and assess their efficacy
using simulated observations of the model sky. We find that while the
large-scale distribution can be unbiasedly estimated from the reconstructed
image from the interferometric data, estimates of the power spectrum of the
intensity fluctuations calculated from the image are generally biased. The bias
is more pronounced for diffuse emission. The visibility based power spectrum
estimator, however, gives an unbiased estimate of the true power spectrum. We
conclude that for an observation with diffuse emission the reconstructed image
can be used to estimate the large-scale distribution of the intensity, while to
estimate the power spectrum, visibility based methods should be preferred.
