Sentiment Analysis of Online Media

A joint model for annotation bias and document classification is presented
in the context of media sentiment analysis. We consider an Irish online media data
set comprising online news articles with user annotations of negative, positive or
irrelevant impact on the Irish economy. The joint model combines a statistical model
for user annotation bias and a Naive Bayes model for the document terms. An EM
algorithm is used to estimate the annotation bias model, the unobserved biases in the
user annotations, the classifier parameters and the sentiment of the articles. The joint
modeling of both the user biases and the classifier is demonstrated to be superior to
estimation of the bias followed by the estimation of the classifier parameters.