A collection of observations of a variable y taken at regular intervals over time is called a time series. Economic data and electrical signals are examples of time series. We can think of a time series as providing data points (xi, yi), where xi is the ith observation time and yi is the observed value of y at time xi. If a time series exhibits a linear trend, we can find that trend by determining the regression equation for the data points. We can then use the regression equation for forecasting purposes.
As an illustration, consider the data on the WeissStats site that shows the U.S. population, in millions of persons, for the years 1990- 2013, as provided by the U.S. Census Bureau.
a. Use the technology of your choice to obtain a scatterplot of the data.
b. Use the technology of your choice to find the regression equation.
c. Use your result from part (b) to forecast the U.S. population for the years 2014 and 2015.