Why the definition of Variance is such.
Motivation behind standard deviation?
Why are integers subset of reals? In most programming languages, integer and real (or float, rational, whatever) types are usually disjoint; 2 is not the same as 2.0 (although most languages do an automatic conversion when necessary). In addition to technical reasons, this separation makes sense -- you use them for quite different purposes.  Why did they choose to say $\mathbb{Z} \subset \mathbb{R}$ in math? In other words, why are 2 and 2.0 considered the same?  When you are working in $\mathbb{R}$, does it make any difference whether some elements, eg. 2.0, also belong to $\mathbb{Z}$ or not? What is the proper way to handle data between scenes? I am developing my first 2D game in Unity and I have come across what seems an important question.  How do I handle data between scenes?  There seems to be different answers to this:   Someone mention using , while other people told me this should be used to store other things like screen brightness and so on. Someone told me that the best way was to make sure to write everything into a savegame everytime that I changed scenes, and to make sure that when the new scene loads, get the info from the savegame again. This seemed to me wasteful in performance. Was I wrong? The other solution, which is the one I have implemented so far is to have a global game object that isn't destroyed between scenes, handling all the data between scenes. So when the game starts, I load a Start Scene where this object is loaded. After this ends, it loads the first real game scene, usually a main menu.   This is my implementation:  using UnityEngine; using UnityEngine.UI; using System.Collections;  public class GameController : MonoBehaviour {      // Make global     public static GameController Instance {         get;         set;     }      void Awake () {         DontDestroyOnLoad (transform.gameObject);         Instance = this;     }      void Start() {         //Load first game scene (probably main menu)         Application.LoadLevel(2);     }      // Data persisted between scenes     public int exp = 0;     public int armor = 0;     public int weapon = 0;     //... }   This object can be handled on my other classes like this:  private GameController gameController = GameController.Instance;   While this has worked so far, it presents me with one big problem: If I want to load directly a scene, let's say for instance the final level of the game, I can't load it directly, since that scene does not contain this global game object.  Am I handling this problem the wrong way? Are there better practices for this kind of challenge? I would love to hear your opinions, thoughts and suggestions on this issue.  Thanks I found an explanation for my question here , which suggests that water washes out sebum (special oil, which covers our skin) and water gets into outer layer of now unprotected skin by osmosis. This article also suggests that fingers are not really shriveled - they are water-logged. But is this right? I think I observed many times my wrinkly fingers after swimming, but I never felt that they are water-logged. Any thought on this matter would be highly appreciated. The "I Get It" Reputation Problem Over the past couple of days there have been a few questions about overlapping proposals and questions that could belong on multiple sites:        What is the best practice before / after asking a question if you think your question might be better on another site?  or  If I think my question might belong on multiple sites as per the above posts? How do you run as a different user from the Start Menu in Windows 10? Running an application as a different user (e.g. domain admin account) from the start menu (by shift + right-clicking the application) used to be an option in Windows 7 &amp; XP.  However, I can't find that option in Windows 10. The workaround seems to be either 1) to find the application in Windows Explorer (shift + right-click) or 2) use runas.exe from the command line.  However, in order to use those workarounds, I have look up the executable name first. It's a bit difficult because I don't have the name of every RSAT tool or executable name memorized.  (e.g. "Active Directory Users and Computers" is dsa.msc, "Routing and Remote Acces" is rrasmgmt.msc)  Is there a simpler way to do this? I've used "//" and "\" to create this "W", and have made them into outlines, as I'm trying to give the different layers a colour, as well as having a white space where the lines touch and I would like to remove the top of the second "\".   I'm struggling with the white space at the moment and now I've added a stroke, the fill has decreased. Is there another way I could do this?   I've also tried to use my pen tool to remove the top of the "\" but when using "Path Finder" I cannot find an option to "Minus Forward". I'm a newbie so any advice would be lovely :) Correct user names when tracking /etc/ in git repository and committing as root How to wait in bash for several subprocesses to finish and return exit code !=0 when any subprocess ends with code !=0? How to avoid nested With[]? How to force the user to download a file, not to view it? How to mount an internal HDD on start-up? I have a 500GB internal HDD where I store all my music and photos but it is annoying to manually mount it after a restart and I was wondering how to mount it automatically and make it available to Rhythimbox for playback.  Thanks! How do I  prevent .xsession-errors from eating disk space? Mail App keeps popping up in the background in Mac OS Mojave How to migrate MongoDB 2.4.14 file to MongoDB 3.6? I have a database file from MongoDB 2.4 and we want use this on mongodb 3.6.  note: the file is original from the db path. Not from mongodump. This process is messy as it requires doing so on many of our clients.  Any advice will be welcomed as I'm a bit lost in this process.  Thanks How to type latin small letter c with cedilla I run Ubuntu on a DELL XPS 13 notebook that has an US keyboard configured as US international. After upgrading to version 13.10 I can no loger get a cedilla by typing '+C. Instead, I get a "ć".  What should I do to get a "ç"?  I am using Ubuntu Gnome 13.10 64 bit. Can you eradicate a disease without finding a Cure first? If you eradicate a disease in Pandemic without finding a cure first (ie remove all of one colour from the board) does it remain eradicated or can it still come back unless it has also been cured?  The rules are a bit unclear on this point ... Or I missed the rule that explicitly states this. I'm experiencing a strange problem with Outlook 2019. When viewing a message it only shows the first line. On an HTML message, it stops at the first close paragraph tag. On a plaintext message, it stops at the first newline character. This is true if viewing a message in the reading pane as well as if double-clicking the message to open in its own window. I have the preview pane set to show 3 lines and it does show more of the message so it seems like Outlook can see more of the message than it's rendering in the reading pane. If I use View Source, the underlying data seems fine and the whole message is there. I've tried the following:  Deleting and re-creating the user's mail profile Uninstalling &amp; re-installing Office Creating a new Windows account &amp; connecting Outlook to a different Exchange account than the one that originally exhibited the problem Checked for Windows updates Checked for Office updates  Any ideas what might be causing this? I feel like I've tried everything obvious &amp; I'm striking out on Google. Today I was told a tale by a Unix trainer where the root password got leaked to the students, and one of the fellas removed the execute permission from /usr/bin/chmod itself. How do you recover chmod in this case and make it executable again? Let's say getting it from an external source or recompiling it is not a preferable option, is there some smart hack that can recover this chmod itself?   Note that this happened a long time ago and I'm not looking for a solution for some current problem, just curious about what ways Unix provides us around such an issue. How are reserved and formal synonyms? In the dictionary reserved means - not revealing emotions and formal means - prim or stiff. I saw they were synonym in the Google dictionary. What makes these two words similar, I wonder?