title: Analysis of PubMed User Sessions Using a Full-Day PubMed Query Log: A Comparison of Experienced and Nonexperienced PubMed Users.
abstract: BACKGROUND
  PubMed is the largest biomedical bibliographic information source on the Internet. PubMed has been considered one of the most important and reliable sources of up-to-date health care evidence. Previous studies examined the effects of domain expertise/knowledge on search performance using PubMed. However, very little is known about PubMed users' knowledge of information retrieval (IR) functions and their usage in query formulation.
  
  
  OBJECTIVE
  The purpose of this study was to shed light on how experienced/nonexperienced PubMed users perform their search queries by analyzing a full-day query log. Our hypotheses were that (1) experienced PubMed users who use system functions quickly retrieve relevant documents and (2) nonexperienced PubMed users who do not use them have longer search sessions than experienced users.
  
  
  METHODS
  To test these hypotheses, we analyzed PubMed query log data containing nearly 3 million queries. User sessions were divided into two categories: experienced and nonexperienced. We compared experienced and nonexperienced users per number of sessions, and experienced and nonexperienced user sessions per session length, with a focus on how fast they completed their sessions.
  
  
  RESULTS
  To test our hypotheses, we measured how successful information retrieval was (at retrieving relevant documents), represented as the decrease rates of experienced and nonexperienced users from a session length of 1 to 2, 3, 4, and 5. The decrease rate (from a session length of 1 to 2) of the experienced users was significantly larger than that of the nonexperienced groups.
  
  
  CONCLUSIONS
  Experienced PubMed users retrieve relevant documents more quickly than nonexperienced PubMed users in terms of session length.
authors.affiliation: Department of Health Management and Informatics, School of Medicine, University of Missouri, Columbia, MO, United States. yooil@health.missouri.edu.
authors.forename: Illhoi
authors.identifier: http://orcid.org/0000-0003-2536-3660
authors.initials: I
authors.lastname: Yoo
authors.forename: Abu Saleh Mohammad
authors.identifier: http://orcid.org/0000-0002-8956-1466
authors.initials: AS
authors.lastname: Mosa
keywords: MEDLINE; PubMed; PubMed query log; experienced users; information retrieval; nonexperienced users