What might be a lurking variable between percentage of the p

What might be a lurking variable between percentage of the population with a cell phone and violent crime rate?

a. overall cell phone signal strength

b. the average cell phone\'s effectiveness as a weapon

c. the economy

d. the police

Solution

The value of linear correlation -0.918 indicates a strong negative relation between the two variables. Thus, it is true that increasing the percentage of the population that has a cell phone will decrease the violent crime rate.  

b. the average cell phone\'s effectiveness as a weapon may be a lurking variable between percentage of the population with a cell phone and violent crime rate.