# Goddammit, learn the difference between correlation and causality!! **URL:** \ **Category:** The BBQ Pit\ **Created:** [July 25, 2002, 1:41pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759 "2002-07-25T13:41:44Z")\ **Posts on this page:** 13\ **Page:** 2
**Author:** ![partly\_warmer](https://avatars.discourse-cdn.com/v4/letter/p/bc8723/32.png) [@partly\_warmer](https://boards.straightdope.com/u/partly_warmer)\ **Post date:** [July 26, 2002, 1:52am UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/21 "2002-07-26T01:52:00Z")
> [@](#): > > \*Originally posted by BlinkingDuck \* > \*\*I am a statistician… > > Your idea of keeping a stat man on staff won’t work. They’ll just be bypassed because they would spoil the story. Even where I work, I am sometimes bypassed because they know I’ll find their wonderful conclusion to not be true.\*\* How do they justify themselves, passing your opinion by? We don’t have time for a study? There are other factors besides stastical ones? There’s not enough data to form a basis for analysis? In all these cases, it seems like the logical answer (which I realize they’ll wiggle out of) is: “I’m the statistician, if I can’t create a reliable analysis, I’ll tell you so–it’s not your job to assess a situation in my area of expertise.” I took statistics in college. What impressed me is how the majority of people can’t work even with implications of simple figures. Do you intentionally “dumb down” results to make them more palatable? How? ---
**Author:** ![The\_Ryan](https://avatars.discourse-cdn.com/v4/letter/t/7feea3/32.png) [@The\_Ryan](https://boards.straightdope.com/u/The_Ryan)\ **Post date:** [July 26, 2002, 1:58am UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/22 "2002-07-26T01:58:23Z")
> [@](#): > > \*Originally posted by sailor \* > \*\*- Couples who lived together before marrying had a greater chance of getting divorced than those who didn’t > > - Correlation does not imply causality > > - Nope, but the correlation remains and for some decisions the correlation is all that is relevant. \*\* Would you decide your living arrangements on the basis of statistics? ---
**Author:** ![Dangerosa](https://avatars.discourse-cdn.com/v4/letter/d/22d042/32.png) [@Dangerosa](https://boards.straightdope.com/u/Dangerosa)\ **Post date:** [July 26, 2002, 11:33am UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/23 "2002-07-26T11:33:08Z")
> [@](#): > > \*Originally posted by partly\_warmer \* > \*\*How do they justify themselves, passing your opinion by? We don’t have time for a study? There are other factors besides stastical ones? There’s not enough data to form a basis for analysis? > > \*\* The company I work for is a Six Sigma believer - and I’m a Six Sigma Brown Belt. Despite being math illiterate, I’ve had to get through an understanding of stats…and know exactly how they justify themselves… “You need how many samples for that? We can’t do that” “Yes, but there is still a chance you are wrong - that’s what you are telling us - and we like this answer.” “Do you know how expensive that DOE would be - we can’t just change our machines like that?” “We need answers now, we don’t have time to gather data and run an analysis.” ---
**Author:** ![partly\_warmer](https://avatars.discourse-cdn.com/v4/letter/p/bc8723/32.png) [@partly\_warmer](https://boards.straightdope.com/u/partly_warmer)\ **Post date:** [July 26, 2002, 12:40pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/24 "2002-07-26T12:40:21Z")
> [@](#): > > \*Originally posted by Dangerosa \* > \*\*I …know exactly how they justify themselves… > > “You need how many samples for that? We can’t do that” > > “Yes, but there is still a chance you are wrong - that’s what you are telling us - and we like this answer.” > > “Do you know how expensive that DOE would be - we can’t just change our machines like that?” > > “We need answers now, we don’t have time to gather data and run an analysis.” \*\* Ha, ha! whoops… i suppose they weren’t trying to be funny? So, I’d answer (providing my aunt was on sleeping terms with the CEO). "Hmm. There isn’t enough time to collect conclusive data, and yet you want to commit the company’s resources to this project? Of course, there’s a possibility that my study is wrong, but there’s an even greater probability your plan is. It is expensive to change our machines, unfortunately, our competition made the changes six months ago. I realize you need answers soon, but the only ones that are available now would probably send the company into bankruptcy." ---
**Author:** ![Dangerosa](https://avatars.discourse-cdn.com/v4/letter/d/22d042/32.png) [@Dangerosa](https://boards.straightdope.com/u/Dangerosa)\ **Post date:** [July 26, 2002, 1:29pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/25 "2002-07-26T13:29:59Z")
Well, except in some cases they are right. To get 3000 samples required to find a change in the defect rate could be cost prohibitive if the defect rate isn’t costing you that much to begin with, but it costs you $4 million to retool - or a complete plant shutdown and restart - which costs millions in lost productivity. And sometimes companies spend far too much time and effort doing statistical analysis on really simple process problems - it takes time to gather and analyze data - it take very little time to realize that the reason your sales have dropped is that the store next door is selling everything you sell for 30% less - don’t need to do a lot of statistics there - yet you’d be surprised and the number of projects that we spend time gathering statisical data on when there is an obvious process change that could fix the issue in one quick step. ---
**Author:** ![CRorex](https://avatars.discourse-cdn.com/v4/letter/c/dfb087/32.png) [@CRorex](https://boards.straightdope.com/u/CRorex)\ **Post date:** [July 26, 2002, 5:07pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/26 "2002-07-26T17:07:04Z")
The general public has the same understand and grasp of statistics as they do of science. And is it any wonder why they get it wrong most of the time ☹ ---
**Author:** ![Rilchiam](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@Rilchiam](https://boards.straightdope.com/u/Rilchiam)\ **Post date:** [July 27, 2002, 12:58pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/27 "2002-07-27T12:58:10Z")
Well, sometimes relationships just run their course. A couple might date for a year, live together for three years, marry, then divorce after another eight years. They might also date for a year, marry, then divorce after eleven years. Same thing. (Yes, I know that’s not all there is to it; just saying that a lot of people marry, thinking they’ll be together forever, and it doesn’t happen. I’m not yet convinced that living together first dooms a marriage.) And although this is not Cafe Society, I must post the Simpsons dialogue that came to mind while I was reading the OP: Homer: Not a bear in sight. The Bear Patrol must be working like a charm. Lisa: That’s spacious reasoning, Dad. Homer: Thank you, dear. Lisa: By your logic I could claim that this rock keeps tigers away. Homer: Oh, how does it work? Lisa: It doesn’t work. Homer: Uh-huh. Lisa: It’s just a stupid rock. Homer: Uh-huh. Lisa: But I don’t see any tigers around, do you? ``` [Homer thinks of this, then pulls out some money] ``` Homer: Lisa, I want to buy your rock. ``` [Lisa refuses at first, then takes the exchange] ``` ---
**Author:** ![NardoPolo](https://avatars.discourse-cdn.com/v4/letter/n/ecae2f/32.png) [@NardoPolo](https://boards.straightdope.com/u/NardoPolo)\ **Post date:** [July 28, 2002, 12:08pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/28 "2002-07-28T12:08:26Z")
> [@](#): > > \*Originally posted by BlinkingDuck \* > \*\*Your idea of keeping a stat man on staff won’t work. They’ll just be bypassed because they would spoil the story. Even where I work, I am sometimes bypassed because they know I’ll find their wonderful conclusion to not be true. \*\* I’m in the same boat. It’s a sad commentary that “The scientific truth” is rarely a match for “The attention-getting PR quote”. The other pet peeve I’ve had is watching managers ask statisticians for a specific answer. “I want to say that this and that are related.” Well, the data says they’re not. “What if we look at it this way instead?” Still no. “How about this way?” Nope. (repeat until required conclusion is found) ---
**Author:** ![Koxinga](https://avatars.discourse-cdn.com/v4/letter/k/4af34b/32.png) [@Koxinga](https://boards.straightdope.com/u/Koxinga)\ **Post date:** [July 28, 2002, 12:26pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/29 "2002-07-28T12:26:56Z")
> [@](#): > > \*Originally posted by Necros \* > \*\*I dunno, **Doghouse Reilly**. I’ll bet you that every one of those people consumed some sort of liquid before they died. I think that the “drinking liquids causes death” idea is an important avenue of investigation that the Onion ignored. \*\* You may be onto something there, **Necros** –since such liquids almost inevitably contain some amount of [Dihydrogen Monoxide](http://www.dhmo.org/). This linked page includes a section entitled “FAQ: DHMO and Cancer”, which states: > [@](#): > > The causative link between Dihydrogen Monoxide (DHMO) and Cancer is currently not established, although a significant amount of evidence seems to suggest that DHMO at least plays a role in the formation of cancer . . . What is known about these cancers is that Dihydrogen Monoxide is found in detectable and biologically significant levels in virtually all tumors and other cancerous and pre-cancerous growths. ---
**Author:** ![5-HT](https://avatars.discourse-cdn.com/v4/letter/5/f19dbf/32.png) [@5-HT](https://boards.straightdope.com/u/5-HT)\ **Post date:** [July 28, 2002, 8:48pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/30 "2002-07-28T20:48:33Z")
This just in: Journalist slain in parking lot ambush by lurking variable 🙂 ---
**Author:** ![tomndebb](https://avatars.discourse-cdn.com/v4/letter/t/b9e5f3/32.png) [@tomndebb](https://boards.straightdope.com/u/tomndebb)\ **Post date:** [July 28, 2002, 10:14pm UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/31 "2002-07-28T22:14:08Z")
> [@](#): > > “We need answers now, we don’t have time to gather data and run an analysis.” Business systems programming works the same way. We have a saying to cover this situation (although we get ignored, anyway–management is generally not much concerned with reality): – You WILL do the analysis. You can do it ahead of time and reduce costs by building it right, or you can do it during testing or after implementation when the costs of correction will be astronomical, but you WILL do the analysis for the system. ---
**Author:** ![Dave\_D](https://avatars.discourse-cdn.com/v4/letter/d/49beb7/32.png) [@Dave\_D](https://boards.straightdope.com/u/Dave_D)\ **Post date:** [July 29, 2002, 5:56am UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/32 "2002-07-29T05:56:58Z")
> [@](#): > > \*Originally posted by CRorex \* > \*\*The general public has the same understand and grasp of statistics as they do of science. > > And is it any wonder why they get it wrong most of the time ☹ \*\* I guess then people teaching statistics should use that old rape/ice cream example. Idiots might get ice cream banned in the US and I like ice cream.(Am I assuming too much in thinking everybody has heard that rape/ice cream statistics example?) ---
**Author:** ![ataraxy22](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ataraxy22/32/307_2.png) [@ataraxy22](https://boards.straightdope.com/u/ataraxy22)\ **Post date:** [July 29, 2002, 6:24am UTC](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759/33 "2002-07-29T06:24:47Z")
Maybe next it will be reported that “correlation causes causality”. [Previous page](https://boards.straightdope.com/t/goddammit-learn-the-difference-between-correlation-and-causality/120759.md?page=1)