Abstract
Crowdsourcing is a technique that aims to obtain data, ideas, and funds, conduct tasks, or even solve problems with the aid of a group of people. It's a useful technique to save money and time. The quality of data is an issue that confronts crowdsourcing websites; as the data is obtained from the crowd, and how they control the quality of data. In some of the crowdsourcing websites they have implemented mechanisms in order to manage the data quality; such as, rating, reporting, or using specific tools. In this paper, five crowdsourcing websites: Wikipedia, Amazon Mechanical Turk, YouTube, Rally Fighter, and Kickstarter are studied as cases in order to identify the possible quality assurance methods or techniques that are useful to represent crowdsourcing data. A survey is conducted to gather general opinion about the range of reliability of crowdsourcing sites, their passion and contribution to improve the contents of these sites. Combining those to the available knowledge in the crowdsourcing research, the paper highlights the factors that influence the data quality in crowdsourcing.