Carrying out research and development on usage search engines is an interdisciplinary effort that requires expertise from information retrieval, information visualization and interface design, as well as domain knowledge from computer linguistics.
to statistically estimate the per-individual effect, we compare the ratio of correct answers among all answers when the search engine was used to the ratio when it was not used (note that this includes the questions where the engine was allowed but was not used; i.e., columns "manually" and "but not used" in table 1).