Explain why a correlation between two variables does not necessarily imply that one variable causes the other to vary as it does. Give an example.
I'm looking for specific, real cases in which a causal relationship was inappropriately inferred from evidence of a correlation.   Specifically, I'm interested in examples that meet the following criteria:   Existence of the causal relationship was accepted as fact widely enough to have notable effects (on public policy, discourse, individual decisions, etc.). The link was inferred solely on the basis of correlative evidence (perhaps along with the existence of a coherent but unproven causal mechanism).  Causality has been objectively falsified or at least called into serious doubt.   The two examples that came to mind for me aren't quite ideal:   Sodium intake and blood pressure: As I understand it, it has since been determined that salt intake only increases blood pressure in sodium-sensitive individuals. The existence of a valid causal relationship (although not quite the one that was originally accepted) make this example less compelling. Vaccines and autism: I may have the background wrong, but I believe this link was surmised on the basis of both correlations and (fraudulent) experimental evidence. This example is weakened by the fact that (fake) direct evidence existed.   Note: I've seen this similar question:    My question differs primarily in that it focuses on notable, real-world examples and not on examples in which a causal link is clearly absent (e.g., weight and musical skill).
Join tables from two different server Python re.sub with a flag does not replace all occurrences Running tcpdump starts ssh flood I have runtime Linux running in a PLC. My development machine is running Ubuntu 14.04. The PLC and the development machine are connected through a five port switch. I ssh to PLC from my development machine to transfer executable of a networking application that I develop on my development machine.   I run tcpdump on PLC to debug the kind of packets my network application is receiving BUT as soon as I start tcpdump, there starts a flood of ssh sync and acks back and forth from my ubuntu machine to the PLC. The LED lights of ethernet controller of PLC as well on the switch start blinking rapidly. The flood overwhelms the PLC and it almost dies down while all other packets get dropped. It feels like a DOS attack whenever I run tcpdump but as soon as I stop tcpdump, everything calms down and gets back to the normal.   I would like know remedy on this problem and why it happens?     Any help would be appreciated. What is your favorite method to handle errors in Bash?  The best example of handling errors I have found on the web was written by William Shotts, Jr at .   He suggests using the following function for error handling in Bash:  #!/bin/bash  # A slicker error handling routine  # I put a variable in my scripts named PROGNAME which # holds the name of the program being run.  You can get this # value from the first item on the command line ($0).  # Reference: This was copied from &lt;http://www.linuxcommand.org/wss0150.php&gt;  PROGNAME=$(basename $0)  function error_exit {  #   ---------------------------------------------------------------- #   Function for exit due to fatal program error #       Accepts 1 argument: #           string containing descriptive error message #   ----------------------------------------------------------------       echo "${PROGNAME}: ${1:-"Unknown Error"}" 1&gt;&amp;2     exit 1 }  # Example call of the error_exit function.  Note the inclusion # of the LINENO environment variable.  It contains the current # line number.  echo "Example of error with line number and message" error_exit "$LINENO: An error has occurred."   Do you have a better error handling routine that you use in Bash scripts? Some kind of + (singular or plural)? I have a question about using the phrase "some kind of _".  Is it incorrect to say "some kind of + plural noun"?     For example, is it wrong to say "are these rock-like things some kind of chocolates?"   I didn't use "kinds" and that kind of adds to my question. Is "kind" always plural, like "some kinds of chocolates"? Because although I'm using "some", it feels like "kind" shouldn't be a countable noun.  Anyway, I don't think I've heard of "some kind of + plural", but I think it makes more sense then using singular, since I think chocolates are countable. Please help! I recently got my Blacksmithing skill to 100. Now in the skills menu I can press space to make it Legendary, which will put it back to a skill level of 15 and reset my perks.  I am wondering: What benefit is there from making a skill Legendary apart from being able to level up the skill more thus having infinite levels? File being used by another process after using File.Create() I'm trying to wrap my head around the math/physics of how illuminance on the film/sensor plane remains equal for a given f-number regardless of the focal length of the lens.  Since a longer lens will have a larger entrance pupil at a given f-stop than a shorter lens at the same f-stop, how can the light falling on the film/sensor be equivalent?  Empirically, I know this to be true.  Say I take an incident meter reading (not reflected/TTL) off my subject, and get f/5.6 at 1/100s, I'll get proper exposure at the point at which i took the meter reading with that setting whether I use a 50mm lens or a 200mm lens (obviously composition will be different).    Wikipedia's  reads:     A 100 mm focal length f/4 lens has an entrance pupil diameter of 25   mm. A 200 mm focal length f/4 lens has an entrance pupil diameter of   50 mm. The 200 mm lens's entrance pupil has four times the area of the   100 mm lens's entrance pupil, and thus collects four times as much   light from each object in the lens's field of view. But compared to   the 100 mm lens, the 200 mm lens projects an image of each object   twice as high and twice as wide, covering four times the area, and so   both lenses produce the same illuminance at the focal plane when   imaging a scene of a given luminance.   I'm not sure I agree with the explanation on wikipedia.  The film/sensor doesn't care how big the image is that falls outside the bounds of the sensor; the film/sensor "sees" what it sees, and that's it. Is the motivation behind the introduction of measure theory the Lebesgue integral? In order to evaluate such an integral we need the length of each of the horizontal strip of width $h$. I have a question here. Why do we need such a general concept of measure? Length is a kind of measure, but why did Lebesgue think of so general a concept of "measure" when he just needed the length to evaluate his integrals? Is there any other motivation behind this ? Windows Batch recursive delete old files What are your favorite English language tools? To prevent myself from asking an obvious, silly question multiple times: What are the English language tools you found most useful?  I found  extremely useful for looking up .   Please, one tool per answer. How to copy a dictionary and only edit the copy Delayed eraser experiment (Kim experiment) Will I receive an interference pattern on D0 detector   if D1, D2, D3, D4 exist in the set up of the experiment, but they are thousands of light years far? Simply, to set up the experiment so that I detect all of the signal photons on D0 before I detect any of idler photons! This is difficult for me to explain, but how do I put words over a symbol? For instance, I want to add words over an equal sign. Anyone know the command/syntax for that?  Also adding ^ doesn't cut it..., I want the text to appear ON TOP. It's a really simple question. However I didn't see it in books and I tried to find the answer on the web but failed.  If I have two independent random variables, $X_1$ and $X_2$, then I define two other random variables $Y_1$ and $Y_2$, where $Y_1$ = $f_1(X_1)$ and $Y_2$ = $f_2(X_2)$.  Intuitively, $Y_1$ and $Y_2$ should be independent, and I can't find a counter example, but I am not sure. Could anyone tell me whether they are independent? Does it depend on some properties of $f_1$ and $f_2$?  Thank you. Is there an unsubdivide function in Blender? I am wondering if there is a modifier or tool that will essentially undo a subsurf or subdivide command. Is there a way to mix LIKE operator with IN ? Something Like  SELECT Id FROM Account WHERE Name LIKE IN:nameList   Where nameList is list of String? Is this is possible ? (I can make a dynamic query by doing OR with all the elements, but was looking for a more elegant way to do this) Lightning Community Does Not Support pubsub for Lightning Web Components? Has anyone successfully used the pubsub module from lwc-recipes to enable inter-component communication in a Lightning Community?  The registerListener function in the pubsub module throws an error because the pageRef property is undefined.  Or is pubsub designed for Lightning Experience only? Is there an AutoHotKey for Ubuntu? I would like to simulate keyboard combinations.  I am able to do this on Windows with AutoHotKey.  Is there an equivalent app for Ubuntu? I want to kill a whole process tree.  What is the best way to do this using any common scripting languages? I am looking for a simple solution.