Example: Cell Phone Usage

Click here to open an associated Mathcad worksheet:

This example investigates power and exponential fits of a data set with a steep upward trend. Interpolated and extrapolated values are compared for the two best fits.

The following table shows the rapid growth of the use of cellular telephones in the U.S.

Year Number of Customers (millions) 1985 0.3 1986 0.7 1987 1.2 1988 2.0 1989 3.5 1990 5.2 1991 7.5 1992 11.0 1993 16.0 1994 24.1 1995 33.8 1996 44.0 1997 55.3 1998 69.2 1999 86.0

Data from the Cellular Telecommunications Industry Association.