“…This is usually the time from when a user starts a specific search task till its end. In contrast to measuring user-efficiency, response time has been used to measure system-efficiency (Dong and Su, 1997;Johnson et al, 2003). Additionally, user effort has been measured in different ways: number of search terms used in a specific task (Dunlop, 1986); number of commands used (Dunlop, 1986), and also number of queries issued to complete a specific task (Su, 1998).…”