This paper examines the problem of locating outlier columns in a large,
otherwise low-rank matrix, in settings where {}{the data} are noisy, or where
the overall matrix has missing elements. We propose a randomized two-step
inference framework, and establish sufficient conditions on the required sample
complexities under which these methods succeed (with high probability) in
accurately locating the outliers for each task. Comprehensive numerical
experimental results are provided to verify the theoretical bounds and
demonstrate the computational efficiency of the proposed algorithm.