Online Crowdsourcing

With the success of modern internet based platform, such as Amazon Mechanical Turk, it is now normal to collect a large number of hand labeled samples from non-experts. The Dawid- Skene algorithm, which is based on Expectation- Maximization update, has been widely used for inferring the true labels from noisy crowdsourced labels. However, Dawid-Skene scheme requires all the data to perform each EM iteration, and can be infeasible for streaming data or large scale data. In this paper, we provide an online version of Dawid- Skene algorithm that only requires one data frame for each iteration. Further, we prove that under mild conditions, the online Dawid-Skene scheme with projection converges to a stationary point of the marginal log-likelihood of the observed data. Our experiments demonstrate that the online Dawid- Skene scheme achieves state of the art performance comparing with other methods based on the Dawid- Skene scheme.