So what's the worst case of "correlation equals causation" you've come across?

Old joke: A man comes out of a bar late at night and sees a badly intoxicated guy on his hands and knees under a street light. The first man goes over to the second and asks him what’s wrong:

Drunk Guy: “I dropped my car keys”

Samaritan: “Do you know about where?”

Drunk Guy: <waves at dark corner of parking lot> “Somewhere out there”.

Samaritan: “Then why are you looking here?”

Drunk Guy: “If they aren’t here, I’m never going to find them.”

I* got the flu once, the day after getting a flu shot, so I’ll never have a flu shot again. :smack:

*Not me, but a real person I know. It was not possible her flu was from any other source, since she was sure she hadn’t been around any sick people; ergo, the flu shot had to have caused it no matter what they say.

I’ve met several people who believe that, and/or that their bad cold is proof that flu shots don’t work. I don’t know how many of the latter have told me I must have the flu because I had symptoms that match a bad cold, not the flu. Of course, these are the same people who think the “stomach flu” is a type of influenza too.

I got that all the time when I was a kid. Having spent my adult life as a cook, I’ve looked back at some of my mother’s food-handling practices back then and strongly suspect it was food poisoning, not “stomach flu”.

If I get intestinal distress (nauseau, diarrhea, vomiting), I usually blame the food I last ate (and lose my desire to ever eat it again) rather than the food I ate 24 hours previously, which supposedly is the most likely culprit.

The mother of one of my neighbors growing up said that an earthquake she’d seen on a news show had been caused by men walking on the moon, which she’d also seen on a news show. She also blamed a thunderstorm on Armstrong and Aldrin.

More recently, I was walking around a lake with my son when we saw a dad with his little boy looking at the water. The little boy asked, “Daddy? What makes the waves?”

The father answered, “It’s the fish and things swimming in the lake.”

My son said, “No, it’s the wind,” but I don’t think they heard him.

Oh dear. What mega-whale causes killer tsunami waves?

The Kraken!

Um, no. Since milk drinking in childhood is equal between drug users and non-users, there is no correlation at all.

That depends on what you mean by “worst case” of course.

[ul]
[li]Do you mean the most ludicrous correlation fallacy upon which time and money was spent?[/li][/ul]
I would suggest that was the neo-puritan idea that consumption of pornographic material causes said consumers to become violent sexual predators, a suggestion that led to the Reagan administration’s formation of the Meese Commision, which was essentially a weekend workshop of Christian leaders and legalists, most of whom were already strongly biassed against adult materials. Not surprisingly, the published results of their work are a slippery slope going from letting kids see porn is harmful to their brains’ to ‘porn makes its viewers violently misogynistic and is related to organized crime’ and, 'laboratory studies# [show]…pornography increases punitive behavior toward women."

For better or worse, the real world surrounding the two administrations that commissioned the porn commissions largely ignored their findings.

*Do you mean the most ludicrous correllation fallacy that has been commercially acted upon, to widespread and global acceptance?

I would nominate the suggestion that spicy foods are fuel for lust, as evidenced by the sensationalized conquests of Don Juan and the scandalous moves of Latin dancers and the romantic and sensual roles so easily portrayed by actors of hispanic descent – all of whom ate the spicy foods that are common in their Latin@ cultures. And, since lust is bad because it leads to the sin of masturbation (which leads to blindness and insanity), America’s youth should be fed relatively bland foods so their libidos will not be stimulated beyond self-control. Therefore, the followers of Sylvester Graham invented Graham Crackers and the Kellogg brothers invented a cereal from ground corn made into toasted flakes, and C.W. Post made a similar cereal from wheat bran (with raisins mixed in).

And there probably isn’t a country on this planet that doesn’t sell some form of bland flaked cereal somewhere (even if it must be imported).

It’s interesting to note that, among their other beliefs (relatively common at the time but seemingly extreme to us now) was the idea that, just like bad germs debilitate a body, undesirable persons (deviants and insane people) reduce the health of a community and undesirable classes of people (Injuns and other heathens) reduce the health of a society.

Which leads me (like a slippery slope) to…

[ul]
[li]Do you mean the most ludicrous correlation fallacy that was politically and socially acted upon, to eventual widespread and global (but, unfortunately, not total) rejection?[/li][/ul]

I would point to the roots of the Eugenics movement: The idea that society as a whole went downhill because we just allowed retarded and insane people to keep on breeding more retarded and insane people. The problem of the time was that insanity was indicated by some behaviors that today’s people find laughable: Dyslexia, poor hearing, nymphomania, homosexuality… What? You can’t get along like everyone else (because you can’t hear or read as well as your peers)? You must be retarded! Let’s rip your organs out to make sure you can’t breed!

That idea crossed the pond and became popular in England as well.

Decades later it was latched onto and became twisted: If homosexuals and other undesirables can be bred out of our society, we should be able to reduce the problems in our society even faster by proactively weeding them out. Never mind the fact that our society’s economic problems are…
A) Brought upon ourselves because the country has to make reparation payments for having started the War to End All Wars, and
B) Being experienced around the world so it’s not just our own economy in trouble.

…just blame the gypsies and Jews because, after all, they’re foreigner types who have been getting blamed for Europe’s social ills for several centuries now.

Such were the unacknowledged seeds of the Holocaust (and later, the Pogroms). And while I’m glad Hitler’s effort was stopped, it’s disenheartening to know that many of those sentiments and correlation fallacies still persist to this day.

–G!

#This conclusion was made despite the fact that they conducted no laboratory research and the laboratory research that was conducted on the matter decades earlier (q.v. Nixon/Johnson commission on pornography) suggests quite the opposite.

@Read ‘Hispanic or descendants of Spanish colonial regions’, not so literally the ‘descendants of Romans.’

We had a parent at my son’s preschool who would not allow her daughter to have dairy products, and pronounced her “allergic” to them, even though she had not been to an allergist.

Apparently, the first time the kid had yogurt, sometime when she was 13 months old, the next day she got an ear infection, and she’d never had one before, so clearly the yogurt caused the infection, and yes, “infection” was the word the mother used.

So we had a triple threat:

Dairy products cause --> “infections” and therefore her daughter had an --> “allergy.”

You do know that abortion also causes infertility, and death right? EVERY woman who had an abortion ends up infertile and/or dead.

“Marriage is the No. 1 cause of divorce.”
I suppose that one is technically true…

The local sports radio host blames the falling NFL rating with the National Anthem Protests.

I think that’s a pretty bold (and wrong) one right there.

Sometimes you hear the claim that experts used to believe that ice cream caused polio. The reasoning is that ice cream consumption peaks in summer, just when new cases of polio peak. Ipso fatso, ice cream causes polio.

The hypothesis was actually a little more subtle but still a classic case of mistaken causation. In the late 1940s and early 1950s at least one doctor believed that a high-sugar diet (including ice cream and soda) made people more susceptible to polio infection. The doctors didn’t believe sugar caused polio; the fact it was caused by a virus was proved about 1909. The experiment that suggested the hypothesis was done on rabbits, not humans, wasn’t particularly convincing, and was never replicated as far as I can tell. cite

I know someone who swears the only reason tobacco causes cancer is because they use sugar to cure it, and “all cancer is caused by sugar intake.”

SDMB thread title:

Shootings near polling places (Azusa, CA)

Increases in autism and diabetes are due to increased organic food sales.

Global warming is caused by a decrease in piracy on the open seas.