Basic Ideas

• Element: Specific subject or object about which the information is collected. Also called a member or observational unit.

• Variable: Any information or data collected from elements. A variable can take different values from different elements. Broken down into qualitative or quantitative variables.

• Quantitative variables can be further broken down into discrete and continuous variables.

• Observation: The value of a variable for an element. Basically a measurement.

• Data Set: A collection of observations of one or more variables.

• Cross-Section Data: Data collected on different elements at the same point in time or for the same period of time.

• Time-Series Data: Data colleced on the same element of the same variable at different points in time or for different periods of time.