Constructs are conceptualized at a theoretical (abstract) level and variables are conceptualized at an empirical (observational) level.
The network showing the overall relationship between constructs is called a nomological network. These tentative and conjectural relationships between constructs are called propositions and are derived by deduction (logic) or induction (observations). Propositions cannot be tested directly as they are between abstract constructs.
Hypotheses are the empirical formulation of propositions as relationships between variables. Propositions and hypotheses are specified in the theoretical level and empirical level respectively as are the constructs and variables. Hypotheses can be tested empirically and rejected if the observations are not supporting the same. This outcome is used to infer if the propositions are valid. Hypotheses should specify directionality and/or causality.
Dr. Selvaraj Vadivelu 