Hypothesis: a formal statement of the expected relationship between two variables. Variables: measures that can take on two or more values. Independent variable: the variable that predicts or is the cause of variation in a dependent variable. Dependent variable: the variable that is expected to vary as a result of changes to te independent variable. Moderating variable: a variable that affects the nature of the relationship between an independent variable and a dependent variable such that the relationship depends on the level of the moderating variable. Mediating variable: a variable that intervenes or explains the relationship between an independent and a dependent variable. Reliability: an index of the consistency of a research subject"s response. Validity: an index of the extent to which a measure truly reflects what it is supposed to measure. Convergent validity: when there is a strong relationship between different measures of the same variable. Discriminant validity: when there is a weak relationship between measures of different variables.