1. People who own more cars tend to live longer than people who own fewer cars. Why is this relationship not evidence that buying more cars increases life expectancy

Car & Life Expectancy positive relationship is not evident, as its due to an interlinking lurking variable ie buyer's affluence.

Explanation:

More cars linked to higher life expectancy, positive correlation between these variables is a spurious correlation. Spurious relationship is a relationship between variables, that appears to be true, when it is actually false.

Given variables' correlation is spurious, as it is not logically correct (evident). It seems to be misleading correct because of a lurking variable, buyer's affluence. Lurking variable affects both independent (causal) & dependent (affected) variable, which creates a statistical illusion of variables' correlation.

In this case, affluence being lurking variable affects both number of cars owned & life expectancy. This seemingly creates a correlation between the non evidently linked variables as 'cars & life expectancy having positive relationship'