What should the relationship between significance and correlation be?
How do you interpret a significant but weak correlation?
Do I have a virus on my phone? A message from an Android app says so I have just received a message from an Android app on my phone saying my phone has been infected with a virus and to click a link to fix the problem.   I'm not sure I trust this, is it possible to have a virus on Android? What are the fundamental differences between the mainstream *NIX shells? What are the fundamental differences between the mainstream *NIX shells and what scenarios might prompt you to use one over the other?  I understand that some of it probably comes down to user preference but I've only ever used Bash and I'm interested to hear where another shell might be useful. Also, is there an impact on user-written shell scripts when running under one shell or another or is it simply a matter of changing the shell at the top of the file?  My instinct says it's not that easy. What's the fixed size of the suggested edit queue? How can I put the computer to sleep from Command Prompt/Run menu? What is the la command? I just mistyped ls as la. Without noticing, I ran it:  tim@Hairy:~$ la detection.sh   output-2.jpg  output-4.jpg  output-6.jpg  output-8.jpg Test1.pdf output-1.jpg   output-3.jpg  output-5.jpg  output-7.jpg  output-9.jpg          tim@Hairy:~$ ls detection.sh   output-2.jpg  output-4.jpg  output-6.jpg  output-8.jpg Test1.pdf output-1.jpg   output-3.jpg  output-5.jpg  output-7.jpg  output-9.jpg    What's the difference between ls and la? Systemd is really slow in comparison to upstart I have been using Ubuntu for a long time now, this is what happened when I use:  Systemd: It performs really bad using systemd: it uses 95% of the CPU all the time and the PC gets really hot. Also it takes a really long time to boot (about 1.5 min, and sometimes it does not boot at all as it has a black screen at boot.)  Upstart: When I tried the upstart options at boot, it performs as expected, booted in seconds, and it was awesome as it should be.  Laptop:   AMD A8 Radeon SSD   Questions:   Why does upstart perform better than systemd? How can I debug systemd? Should I switch to upstart? If yes, how do I do it? Trace of a commutator is zero - but what about the commutator of $x$ and $p$? Operators can be cyclically interchanged inside a trace: $${\rm Tr} (AB)~=~{\rm Tr} (BA).$$ This means the trace of a commutator of any two operators is zero: $${\rm Tr} ([A,B])~=~0.$$ But what about the commutator of the position and momentum operators for a quantum particle? On the one hand: $${\rm Tr}([x,p])~=~0,$$ while on the other hand: $$[x,p]~=~i\hbar.$$ How does this work out? What is a tensor? I have a pretty good knowledge of physics, but couldn't deeply understand what a  is and why it is so fundamental. A big thank you, Tim Post As you may have seen, this was ’s last week at Stack Overflow. To say that he has been a staple of this company for a very long time is an understatement. Tim has served , evangelist, thought leader, anthropologist, psychologist, and mediator for this site for almost as long as it’s been around. For me personally, Tim has been my right hand in this role. He has educated me on the history of our community, been the person I’ve gone to to ask “why is this thing this way?“, bounced ideas off of, collaborated with, and relied on as a steady voice and a thoughtful teammate. We’re all proud to send him off and support him in any way we can in his next role. Tim has agreed to meet with me once a month to talk these things through moving forward and I’m excited to continue getting his feedback on our initiatives and goals. Thank you, Tim, for being such a stalwart here for so long. We’ll miss you, and look forward to sneaking you into our “Among Us” games for as long as we can. We're also excited to see you request to rejoin the ranks of Stack Overflow moderators and continue to be a pillar in the community. terminal: non-english characters I used to be able to copy&amp;paste (or type if I load respective keyboard layout) any kind of characters (eg. é ö ñ ß و 好) in my console/terminal.  Now I bought a new computer and it does not work any more, only English/ASCII characters (but in other programs, e.g. firefox, it still works).  Distribution: Ubuntu. Terminals tried: gnome-terminal, xterm, konsole.  I tried  but after reboot echo $LANG still gives C. I also tried setting Character encoding to Unicode(UTF-8) in the gnome-terminal Terminal-menu - without effect.  Question: How can I get a terminal that is able to deal with non-English characters? How to perform the modular reduce of Rijndael's finite field I am trying to understand how to calculate the modular reduction of Rijndael's finite field.  The example on  page says that {53} • {CA} = {01}, because (11111101111110 mod 100011011) = {3F7E mod 11B} = {01} = 1.  I am able to get to the point where I have 3F7E mod 11B, but cant seem to figure out how the reduction works.        11111101111110 (mod) 100011011      ^100011011             1110000011110       ^100011011             110110101110        ^100011011             10101110110         ^100011011             0100011010            ^100011011 &lt;-- here, right shifted two places?             00000001   From this example, why does it right shift two places at one point?  I also found an example that 0x1b*0xaa equals 0x8c. Trying to solve this myself I get to the point: 0xE0E mod 0x11B   111000001110 ^100011011   11011010110  ^100011011    1010111010   ^100011011     010001100    ^100011011      10010111   This makes it 0x97 Short circuit or disconnect to bypass a compressor Will a PCI Express x16 3.0 card work in a PCI Express x16 slot? I have a motherboard with a PCIexpress x16 slot.  I want to purchase a card called AMD Radeon HD 7770, which uses PCIe version 3.0.  Is that backwards compatible? File Save dialog unreadable I just updated my iMac to Mojave, and am still trying to setup my preferences.  I tried dark mode, but did not like it (half of me apps seem to ignore it anyway).  I switched to light mode, but this too has problems. The File Save dialog shows a list of Directories and existing files, but the latter are very light grey, almost indistinguishable from the background.    I have searched the Preferences menu, but can't seem to find any setting to set normal contrast levels like in High Sierra. How can I restore configuration files? How do I learn where the source file for a given Python module is installed? Is the method different on Windows than on Linux?  I'm trying to look for the source of the datetime module in particular, but I'm interested in a more general answer as well. So, my update to 13.04 didn't go very well. Due to the lack of a decent driver (Yes, i'm unlucky to have a legacy driver which doesn't play nice with the new Xorg.), I had to mess around with stuff to first troubleshoot and afterwards "fix" my system.  I've finally got unity back, but now CtrlAltarrow and CtrlAltShiftarrow don't work anymore. They are bound in "keyboard" > "shortcuts", but nothing happens when I try it. A strange thing is that other keyboard shortcuts, like ctrlaltt to show terminal are still working.  I noticed that CtrlAltarrow doesn't show in the list with "unity shortcuts" (the list that shows when you hold the super key).  Does anyone know how to re-enable this way of workspace switching?  I enabled workspaces in the appearance menu. It doesn't have any effect though. Switching via the workspace-switcher in the unity dash works fine though.  CCSM is installed, but I can't seem to find a way to add keyboard bindings there.     System: ubuntu 13.04 64bit Are there critical hits for spells? Shell Shortcuts in Windows OS Changing the size of the mouse pointer in Ubuntu MATE 18.04 does not work