How to establish and prove causality between two variables?
Statistics and causal inference?
Why are news headlines in present tense if they refer to past events? In news papers we see headings like this  &quot;India signs a pact with Russia&quot; &quot;Sachin hits another century&quot; &quot;Obama wins presidential election&quot;  These are completed events, aren't they? Then, why are these sentences not mentioned in past tense? Is it true that  $$\int_a^b f(x) dx = \int_{f(a)}^{f(b)} f^{-1}(x) dx$$  Just making sure.   If not, how about:  $$\int_a^b f(x) dx = (f(b)-f(a))b - \int_{f(a)}^{f(b)}f^{-1}(x)dx$$   I'm having a hard time concentrating right now, and I'm trying to figure out how to get the area under a curve when the function is inverted. fp - How to keep running sum in variable? I have this code in my LaTeX:   \FPset{totalHours}{0}  \newcommand{\entry}[5]{     \FPeval{totalHours}{(totalHours)+#5}     #1 &amp; #2 &amp; #3 &amp; #4 &amp; #5 \\ }   Where \entry is meant to be an entry in a time log. The 5th argument is a number representing the number of hours in that entry. I want to keep a running total of the hours in a variable I can print later on, totalHours.   This seems to do the \FPeval but then totalHours gets reset to 0 by the next time I write \entry. What is the correct way to keep a running total? Thanks. According to HTML specs, the select tag in HTML doesn't have a readonly attribute, only a disabled attribute. So if you want to keep the user from changing the dropdown, you have to use disabled.  The only problem is that disabled HTML form inputs don't get included in the POST / GET data.  What's the best way to emulate the readonly attribute for a select tag, and still get the POST data? How to prove $a^2 + b^2 + c^2 \ge ab + bc + ca$? How can the following inequation be proven?  $$a^2 + b^2 + c^2 \ge ab + bc + ca$$ My question is pretty simple.  Since $n! \gt n!!$, it's clear by the comparison test that $\sum_{n=0}^\infty \frac {1}{n!!}$ converges.      But what value does the sum converge to? How does one go about determining its value (if possible)? If I design a PC for use as an NPC, how much XP should he give when killed? So from what I understand transistors are one of the most important electronic elements for computers because of TTL (Transistors-Transistors Logic).  Is this true? If so, how exactly does this work? I have heard the terms "logic gate" and "logic block" tossed around. How to call a function in a Twig file Let's say I create a function in a module file:  function _get_test() {   return 'test'; }   How can I call this in any Twig file? For example *.html.twig, page.html.twig, node.html.twig etc.   OR   How can I pass a variable from PHP to Twig and display in any Twig file.  For example *.html.twig, page.html.twig, node.html.twig etc. Movie/TV series with a scene of spiky, black goo growing out of a lab container? There was a scene from a sci-fi horror video, not animated, don't know if it's a movie or TV series, where there was this black goo in a glass container and some scientists were looking at it under a microscope.   The pitch black goo grew and grew so fast, eventually breaking out of the inner box and the scientists that were inside the "inner lab" were begging to get out but the scientists outside that inner lab refused to open the door. The black goo was spiky (had spikes).  It's not any of the "Alien" movies, "The Blob", "Life", or "The Thing". It's not vintage. It was made after 1990, I'm pretty sure. This is a weird phenomenon.  Consider the following code:  \documentclass{article} \begin{document}   $$Z^* \frac{Z^*}{Z^*}$$ \end{document}   It produces the following picture:    The asterisks appear in various places in comparison to the Z. This looks particularly bad in the denominator. Any idea what's behind this? Why is that when I open up my file in blender, the reference picture is gone When you are using a reference picture in blender, do you have to keep it? Do the pictures have to stay in your computer? I sometimes delete my reference images, because I'm on my mother's computer and any file I download has to go away. When opening my blender file the pictures are gone. How can I get my reference images to stay in my blender file even if the original file is deleted? Running "sudo apt-get update" returns connection errors After installing Ubuntu 18.04 from the Windows store I open Bash and want to run sudo apt-get update, but this returns the following errors:  Err:1 http://security.ubuntu.com/ubuntu bionic-security InRelease   Connection failed [IP: 91.189.91.26 80] Err:2 http://archive.ubuntu.com/ubuntu bionic InRelease   Connection failed [IP: 91.189.88.162 80] Err:3 http://archive.ubuntu.com/ubuntu bionic-updates InRelease   Connection failed [IP: 91.189.88.161 80] Err:4 http://archive.ubuntu.com/ubuntu bionic-backports InRelease   Connection failed [IP: 91.189.88.162 80] Reading package lists... Done W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic/InRelease  Connection failed [IP: 91.189.88.162 80] W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-updates/InRelease  Connection failed [IP: 91.189.88.161 80] W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-backports/InRelease  Connection failed [IP: 91.189.88.162 80] W: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease  Connection failed [IP: 91.189.91.26 80] W: Some index files failed to download. They have been ignored, or old ones used instead.   When I open 91.189.91.26 in a browser, it shows the site without a problem.  Previously this worked without any problem, but I did a clean reinstall of Windows and now it doesn't work anymore. It seems some firewall or proxy issue, but I tried with the firewall disabled and I got the same result.  Any idea why this is happening? Maybe it is a 18.04 issue? If so, is it possible to return to 16.04 on Windows 10? Becasue I don't see a uninstall option. drupal 7 + services 3 - inserting nodes with select fields I'm using Drupal 7 + Services 3 to create nodes with POST and JSON. Everything works fine, except field types of select - entity reference select or plain text.  The entity reference uses the autocomplete widget, while the text select is a plain radio button.  This is the format I'm using:  "field_urgency": {     "und": [  {  "value": 1    }   ] } Recommend MVVM or just answer the question? Which is the best way to put function plots into a LaTeX document? When I use TikZ tree with nodes with rounded corners, the connecting lines do not touch the nodes (near corners) but end where would rectangle end. Is there an easy way around it?  \documentclass{standalone} \usepackage{tikz} \begin{document} \begin{tikzpicture} [sibling distance=100]    \node[rectangle, draw, rounded corners = 3]{ }   child { node { } }   child { node { } }   ; \end{tikzpicture} \end{document} ODBC and ADO connection to SQL Server: What protocol is used when connecting to \? Finding an expression for $\tan (a+ b + y)$ which involves only $\tan a, \tan b,$ and $\tan y$. How do I ignore ampersands in a SQL script running from SQL Plus? I have a SQL script that creates a package with a comment containing an ampersand (&amp;). When I run the script from SQL Plus, I am prompted to enter a substitute value for the string starting with &amp;. How do I disable this feature so that SQL Plus ignores the ampersand?