• Summary
  • Contents
  • Subject index

Via 100 entries, 21st Century Psychology: A Reference Handbook highlights the most important topics, issues, questions, and debates any student obtaining a degree in the field of psychology ought to have mastered for effectiveness in the 21st century. This two-volume reference resource, available both in print and online, provides an authoritative source to serve students’ research needs with more detailed information than encyclopedia entries but without the jargon, detail, or density found in a typical journal article or a research handbook chapter. Students will find chapters contained within these volumes useful as aids toward starting research for papers, presentations, or a senior thesis, assisting in deciding on areas for elective coursework or directions for graduate studies, or orienting themselves toward potential career directions in psychology.


The field of psychometrics aims to measure psychological phenomena. Researchers disagree as to whether and how psychological measurement is accomplished. In his letter to the Grand Duchess Christina, Galileo Galilei (1610/1957) stated that the universe has its own language and set of characters. If we wish to understand our universe, we must understand that it “was written in the language of mathematics.” (p. 237). This chapter introduces the field of psychometrics.


When we analyze the roots of the word psychometrics, we find psycho, which means “individual” or “mind,” and metric, which means “measurement.” The field of psychometrics attempts to measure psychological phenomena. A more specific working definition of psychometrics is derived from the field's historical roots. Galileo's philosophy about the importance of numbers is reiterated ...

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