Measurements collected at different time periods are called time series . Time series can easily be plotted with the Time Series Plot See Figure 15 . See Figure 16 . The time series plot appears in Figure 17 . Research might involve individuals or perhaps counties or provinces or countries.
Variables are properties or attributes of units of analysis.
Do not confuse a variable with a specific amount. Sometimes the distinction between dependent and independent variables is arbitrary. Variation may be large or small. This is normally done by using one or more independent variables to explain a dependent variable.