Inferences from correlations

EveryCookCanGovern

If we are told, as X increases Y increases. Can we infer that as Y increases X increases?

lexxx745

No

for example,
as one smokes more, the chance of one getting heart disease goes up

Does that imply, as the chance of one getting heart disease goes up, one is smoking more? No
Why? Because the chance of you getting heart disease could go up independent of smoking more. It could be for other reasons, like eating a ton of junk food.

Logician

No, that could be the reason but it’s not the case that it must be. In other words, correlation does not imply causation. There are 4 different competing explanations as to what could be happening.

1) there could be a third variable (Z) that is causing both X and Y to increase.

2) X could be causing Y to increase.

3) conversely, Y could be causing X to increase.

4) There is no relationship.