Safety critical jobs in fields such as aviation and nuclear power plants require a careful and comprehensive analysis of all factors relevant to critical job performance. Understanding how these factors uniquely and in combination, affect performance requires interconnecting a job performance database with several other information databases. The scientific method is necessary to ensure information quality; to solve problems or project trends; and to correctly evaluate changes in selection, training, performance evaluation, the person-machine interface, or team dynamics. Combining the scientific method with the construction, validation and use of the information databases results in a Scientific Information System (SIS), which joins practical utility with powerful evauations of relevant theories. This book discusses how to blend scientific methods with the broad capabilities of computer database information systems. This synthesis will aid anyone who is trying to explain, predict, or change the behavior of a complex system involving humans. Whilst developed from research on information systems in the aviation industry, the principles and methods are universal and the book provides conceptual guidance for the construction and use of such systems in other domains. The examples clarify the advantages of this type of information system and the enormous potential power for understanding a target system completely and accurately.