Much social science research is designed to test hypotheses (or propositions) about causation. Such hypotheses take the form of an assertion that if something (e.g., some event) occurs, then something else will happen as a result. Among nations, we might assert that population growth causes (or influences) economic growth. Among individuals, we might believe that body weight is influenced by food consumption. In a causal hypothesis, the phenomenon that is explained is called the dependent variable. It is called a variable because we are conceiving of something that can “vary” across a set of cases (e.g., persons or nations); it is called dependent because of the assertion of causation: its value is hypothesized to be dependent on the value of some other variable. In our examples the dependent variables are a nation’s economic growth and an individual’s weight. The other variable in the hypothesis—the one that is expected to influence the dependent variable—is called the independent (or explanatory) variable. Population growth is thought to be an independent variable affecting a nation’s economic growth; a person’s food consumption is conceived as an independent variable influencing his or her weight. There are numerous synonyms for the terms independent and dependent variable in the social sciences. Table 1.1 lists the most common terms.