Fleiss was born in Brooklyn, New York. He attended Columbia College of Columbia University and was awarded a bachelors degree in 1959. He earned an M.S. in biostatistics in 1961 from the Columbia University School of Public Health (now called the Mailman School of Public Health), and a Ph.D. in statistics in 1967 from the Department of Mathematical Statistics in the Columbia Graduate School of Arts and Sciences.

Fleiss began his career as a biostatistician at the Biometrics Research Unit of the New York State Psychiatric Institute. While working at the Psychiatric Institute, he became a professor at the Columbia University School of Public Health.

Fleiss served as head of the Division of Biostatistics at the School of Public Health from 1975 to 1992. Under his leadership, the Division increased in size and stature. Fleiss transformed the Division from a small program consisting chiefly of New Yorkers into a department with international prestige by recruiting top faculty from major institutions around the world.

One of Fleiss's chief concerns was mental health statistics, particularly assessing the reliability of diagnostic classifications, and the measures, models, and control of errors in categorization. He was among the first to notice the equivalence of weighted kappa and the intraclass correlation coefficient as measures of reliability in categorical data (see Fleiss' kappa).

In an influential 1974 paper co-authored with Dr. Robert Spitzer, Fleiss demonstrated that the second edition of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders (DSM-II) was an unreliable diagnostic tool . They found that different practitioners using the DSM-II were rarely in agreement when diagnosing patients with similar problems. In reviewing previous studies of 18 major diagnostic categories, Fleiss and Spitzer concluded that "there are no diagnostic categories for which reliability is uniformly high. Reliability appears to be only satisfactory for three categories: mental deficiency, organic brain syndrome (but not its subtypes), and alcoholism. The level of reliability is no better than fair for psychosis and schizophrenia and is poor for the remaining categories."

The paper by Fleiss and Spitzer led to improvements in diagnostic criteria that were incorporated in the third edition of the Diagnostic and Statistical Manual (DSM-III), which was published in 1980.

Fleiss wrote two textbooks that are considered classics in biostatistics. According to the Institute of Mathematical Statistics, Statistical Methods for Rates and Proportions (1973) continues to be particularly influential in the fields of psychiatry and epidemiology. Design and Analysis of Clinical Experiments (1986) was influential among medical researchers and biostatisticians, with its challenges concerning the planning and interpretation of studies involving human subjects. Fleiss also contributed chapters to more than two dozen books and authored or co-authored more than 200 statistical and scientific papers concerning the application of statistics in fields ranging from psychiatry and cardiology to dentistry.

Among his many honors, Fleiss was given the Mortimer Spiegelman Award by the Statistics Section of the American Public Health Association in 1973. In 1997, the Harvard Institute of Psychiatric Epidemiology and Genetics recognized Fleiss with a Lifetime Contribution Award for his contributions to psychiatric epidemiology and biostatistics.

Books

Selected papers

Joseph Fleiss