Factor analysis was invented in 1904 by Professor Charles Spearman at University College London. Spearman was a psychologist and, for half century, factor analysis largely remained the preserve of psychologists. Latent class analysis was developed by Paul Lazarsfeld at Columbia University in New York in the nineteen fifties and was designed for use by sociologists. Yet both of these techniques, and others like them, are essentially statistical and are now recognised as sharing a common conceptual framework which can be used in a wide variety of fields. It was not until the late nineteen thirties that statisticians, such as M. S. Bartlett, made serious contributions to the field.