ABSTRACT
Any study with a structural equation model (SEM) begins with a focus on the causal and effect constructs that one wishes to study. Each of these constructs must be a variable. In the framework of this book, a variable is a set of attribute states or qualities such that, to any object that may be described in terms of these states or qualities, one and only one member of the set may be assigned at any one time. In other words, there is an implicit schema that objects (e.g., persons) become bearing attributes, that attributes (e.g., blonde, brunette, redhead, brownette) are segregated into sets, each having some characteristic in common such as hair color, and no object may have more than one value of the same attribute at the same time (e.g., Joe is blonde). Frequently, these states or qualities are represented as a given quantity of some attribute and thus have numerical values. For example, Joe weighs 174 pounds.
