Refer to Example 6 concerning spurious correlation.

Replace number of cell phone subscribers with the number of registered motorcycles in millions.

TABLE 10 Variables Showing Spurious Correlation Inmates Cell phones Motorcycles

(mil) (mil) (mil) Year 1.20 55.3 3.8 1997 1.25 69.2 3.9 1998 1.30 86.0 4.2 1999 1.33 109.4 4.3 2000 1.35 128.4 4.9 2001 1.38 140.8 5.0 2002 1.41 158.7 5.4 2003 1.43 187.1 5.8 2004 1.53 207.9 6.0 2005 1.57 233.0 6.2 2006

(a) Create a scatter diagram and identify the kind of association.

(b) Comment on possible lurking variables.