This is one of my favorite things to keep in mind. It reminds that things can happen for reasons that seem apparent but are actually different in reality. I always have trouble coming up with a good example but yesterday I came across one.
I left work early yesterday and hit Tarara Vineyard with a friend. We did the super secret tasting and, really, they actually have very good wine. Not sure where the dislike comes from. But anyway, the point is we were talking to the pourer (who turned out to be the wife of the winemaker) about buttery Chardonnay which I absolutely hate. I call them popcorn butter. Somehow the conversation of oak vs stainless steel came up. Here is the correlation part. When tasting Chardonnays and one is buttery as hell, it always seems to be aged in oak. When tasting a Chardonnay I can stomach it is in stainless steel. So it seemed that the buttery flavor was in part due to the oak. Turns out, it's actually caused when they ferment the wine with the leaves and they normally only do that in oak. Stainless steel is used for a lighter wine so they don't ferment with the leaves. Ta da.
So there you go. The correlation was that the Chardonnay was fermented in oak therefore it had the buttery taste. Turns out the oak wasn't the cause thus the saying: Correlation does not equal causation.
My office hours are 3 pm to 3:05 pm every other Tuesday if there are any questions. ;)