To begin our coverage of SEM, we'll discuss the conceptual basis of latent variables and their manifest (measured) indicators. The diagram below, which I developed several years ago, provides an "everyday" illustration.
A key idea that we'll discuss throughout the course is that latent variables are error-free.
There are some additional analogies that can be drawn upon:
In Freudian psychology, a distinction is made between the latent and manifest content of dreams.
In biology, a distinction is made between genotype and phenotype.
The book Does Measurement Measure Up?, by John Henshaw, provides a concise summary of how observable, measurable manifestations are used to infer underlying, unobservable propensities: "Aristotle and others have contrasted the observed behavior of an individual with the underlying capacity on which that behavior depended. Intelligence, as one of those underlying capacities, is an ability that may or may not always be observed in everyday life. This underlying capacity must be deduced from observed behaviors" (p. 92).
