: This refers to the consistency and precision of a measure. Nunnally emphasized internal consistency , popularized through the use of Cronbach’s alpha
Given the book's enduring relevance, many researchers and students seek digital copies for convenient reference. Several options exist for accessing "Psychometric Theory" in PDF format, though copyright and legal considerations are important to keep in mind.
: The consistency of a measure. Nunnally is famously associated with the rule of thumb that a Cronbach’s alpha is the minimum acceptable level for early-stage research.
A threshold of .80 is preferred for well-established scales.
After the war, Nunnally pursued an academic career and eventually joined Vanderbilt University in 1960, where he quickly rose to become the second chair of the psychology department. He served as department chair from 1961 to 1964 and again from 1967 to 1970. Beyond "Psychometric Theory," Nunnally was a prolific scholar who authored 66 papers, accumulating over 1,500 indexed citations across developmental and educational psychology, cognitive neuroscience, and experimental psychology. His work on attitudes toward mental health, particularly his 1961 book "Popular Conceptions of Mental Health," and his numerous publications on factor analysis and measurement methods established him as a leading figure in quantitative psychology. Nunnally passed away in August 1982, but his intellectual legacy endures through his written work.
Before delving into the book itself, it is important to understand the man behind the work. Jum Clarence Nunnally was born in Birmingham, Alabama, on February 1, 1924. He completed high school in 1942 and subsequently joined the United States Army Air Corps. It was during his military service that Nunnally developed his interest in psychometrics: he credited his score on the Army General Classification Test (AGCT)—which qualified him for officer training and eventually earned him his pilot's wings—with awakening his curiosity about psychological measurement. This personal experience with standardized testing would prove formative for his later scholarly pursuits.