“If We Only Knew How You Feel”—A Comparative Study of Automated vs. Manual Classification of Opinions of Customers on Digital Media

The Web development has drastically changed the human interaction and communication, leading to an exponential growth of data generated by users in various digital media. This mass of data provides opportunities for understanding people’s opinions about products, services, processes, events, political movements, and organizational strategies. In this context, it becomes important for companies to be able to assess customer satisfaction about their products or services. One of the ways to evaluate customer sentiment is the use of Sentiment Analysis, also known as Opinion Mining. This research aims to compare the efficiency of an automatic classifier based on dictionary with the classification by human jurors in a set of comments made by customers in Portuguese language. The data consist of opinions of service users of one of the largest Brazilian online employment agencies. The performance evaluation of the classification models was done using Kappa index and a Confusion Matrix. As the main finding, it is noteworthy that the agreement between the classifier and the human jurors came to moderate, with better performance for the dictionary-based classifier. This result was considered satisfactory, considering that the Sentiment Analysis in Portuguese language is a complex task and demands more research and development.