In order to study the efficacy of the ranked set sampling (RSS), as an alternative procedure, for estimation of the proportion of children aged 12-23 immunized against measles vaccine, a study is conducted in slum and non-slum regions of Guwahati, the capital of Assam, India. The RSS-based approach in the cases of both perfect and imperfect rankings is compared with its counterpart simple random sampling (SRS). The results revealed that estimates based on RSS with set size (4) are very close to Census report for Assam (2012) and has less variability than the SRS estimator. RSSbased estimates for different choices of probability of ranking error (ρ) are not only more accurate but are more precise and efficient than the SRS procedure, and also suggest that a the procedure of RSS better than the classical SRS.