Consider a large number of countries around the world. There is a positive correlation between the number of cell phones per person, x, and the average life expectancy, y. Does this mean that we could increase the life expectancy in Rwanda by shipping cell phones to that country
A. No: if the correlation were negative we could accept that conclusion, but this correlation is positive.
B. No: the positive correlation just shows that richer countries have both more cell phones and higher life expectancies. We don't know if there is causation.
C. Yes: the positive correlation means that if we ship do more cell phones we can expect an increase in life expectancy.
D. Yes: the correlation says that as cell phones go up, it causes life expectancy to go up.
