I am a beginner in statistics so I would like some help with literature. I have a linear model $Y= b_0 + b_1 X^2$ Intercept $b_0$ is not significant (sig: 0,09 > 0,05) but $b_1$ is very significant. I cannot find any literature to support the fact that it is not a big problem for the intercept being zero and also I am not sure I am right.   I understand there's another similar question but I wonder if anyone has an official paper or book that, states the answer to my question. I haven't found something answering exactly that.
I built a model of multiple linear regression to predict the revenues at the box office of a movie: the variable $Y$ is revenue while the variables $X$ are two: Activity (number of tweets per day) and sentiment (connotation of these tweets).  The problem is that the intercept is not significant. I thought of a possible explanation: the intercept in practice is the value of the variable $Y$ when the variables $X$ assume values of 0; but because of the very strong development of social networks, it is virtually impossible not to have even a tweet (and then a wave of activity) about a movie that just came out, I thought that the significance or not the intercept could be neglected because the assumed value has no meaning in reality (a tweet of 0 would never be satisfied, given the market today). In this way, I consider the intercept a mere constant for the calculation of the line, without worrying about its significance (because in some cases would take negative values, which is impossible for revenues).  The interpretation may be correct?
Why isn't my Gravatar image updating? Prove that the additive group $ℚ$ is not isomorphic with the multiplicative group $ℚ^*$. Prove that $ℚ^*_{&gt;0}$ is not isomorphic with $ℚ$. How do I know the script file name in a Bash script? How can I determine the name of the Bash script file inside the script itself?  Like if my script is in file runme.sh, then how would I make it to display "You are running runme.sh" message without hardcoding that? How to set custom DNS server for Chrome browser? I have a local DNS server that resolves all URLs *.domain.tld to 127.0.0.1. Also, I have the production server with the same address *.domain.tld. They have the same names, because subdomains interact with each other, and I have hardcoded domain URLs. I can't change them in the production server.  The problem is to reach the production server from my developer computer without touching the DNS server and /etc/hosts.  I found some options for Chrome such as --dns-server, --host-rules, but none is working. I have Google Chrome 23.0.1271.64 and Chromium 22.0.1229.94 on Ubuntu 12.10 64-bit. I have a vps using Ubuntu 12.04 LTS and I my host corrupted my vps so now it won't boot up. When it boots up it says:  Booting from Hard Disk... error: file not found. grub rescue&gt;   How can I fix/repair this? How to express a polar coordinate for a macro that only accepts space-separated values? \psElectricfield only accepts a coordinate in space-separated values as follows. For example, a charge of -0.1 unit at (-1,0) is written as [-0.1 -1 0]. I have attempted to write in PS notation but it still does not work.  \documentclass{article} \pagestyle{empty}  \usepackage{pst-electricfield,multido} \def\M{2}  \begin{document} \multido{\i=0+30}{12}{% \begin{pspicture*}(-\M,-\M)(\M,\M)     \psElectricfield     [         Q={[-0.1 -1 0][-0.1 1 0][0.1 !\i sin 2 mul \i cos 2 mul]}     ] \end{pspicture*}\newpage} \end{document}   How to express  a polar coordinate for a macro that only accepts space-separated values? We have a Barbarian on our team that very much likes to switch up his weapons; he goes from a Dwarven Hammer, to a pair of Hand-Axes, to occasionally just going bare-fisted. No issues there, he's fairly adept with all 3.  However, I have only just recently picked up on the way that he rolls his attacks for the two Hand-Axes: He rolls the first attack, adds his modifiers etc. Then he rolls the second attack, this time without modifiers, which is all well and good. But I'm not sure if this action uses his bonus action or not, or is considered a separate action (though, being a level 4 Barbarian, he only has one action per turn), or is merely part of the same action.  If we have a look at the Two-Weapon Fighting feature from the Fighter's fighting styles:     Two-Weapon Fighting   When you engage in two-weapon fighting, you can add your ability modifier to the damage of the second attack. (PHB5e p.72)   Similarly, the Dual Wielder feat also uses the Two-Weapon Fighting feat:     Dual Wielder   You master fighting with two weapons, gaining the following benefits:      ...         You can use two-weapon fighting even when the one-handed melee weapons you are wielding aren’t light. (PHB5e p.164, emphasis mine)      So; yes, this gives a bonus to the second weapon attack, but having asked a  to clarify which action this secondary weapon attack belongs to, it was determined that this uses your bonus action;     [...] the second attack requires a bonus action   So after that long winded explanation, here is the question: Without any additional feats, can you wield and use two weapons at once, and if so, how many actions does it require to make a full attack with both weapons in a turn? Infinite series $\sum _{n=2}^{\infty } \frac{1}{n \log (n)}$ What does "calculus" mean? "calculus" and "formal system"  From      a calculus is a formal system that consists of          a set of syntactic expressions (well-formed formulæ or wffs),    a distinguished subset of these expressions (axioms), plus    a set of formal rules that define a specific binary relation on the space of expressions.      From      Formal systems in mathematics consist of the following elements:         A finite set of symbols (i.e. the alphabet), that can be used for constructing formulas (i.e. finite strings of symbols).   A grammar, which tells how well-formed formulas (abbreviated wff) are constructed out of the symbols in the alphabet. It is   usually   required that there be a decision procedure for deciding whether a   formula is well formed or not.   A set of axioms or axiom schemata: each axiom must be a wff.   A set of inference rules.      what is the difference between a formal system, and a calculus, then? I think they are the same? "calculus" and "logic system"  "Calculus" appears in "propositional calculus" and "first-order predicate calculus", which are also called "propositional logic" and "first-order logic" respectively. So I thought "calculus" and "logic" mean the same, and "a logic" is, according to ,      A logical system or, for short, logic, is a formal system together with a form of semantics, usually in the form of model-theoretic   interpretation, which assigns truth values to sentences of the   formal language, that is, formulae that contain no free variables.    But then I saw "calculus" also appears in "lambda calculus", which is also a formal system. I think a lambda calculus isn't a logic system, right? What does "calculus" mean in "lambda calculus"? Furthermore  "calculus" can also mean computational real analysis for first-year college students.   Thanks. What are good learning resources for a LaTeX beginner? C: pointer to struct in the struct definition How can I have a pointer to the next struct in the definition of this struct:  typedef struct A {   int a;   int b;   A*  next; } A;   this is how I first wrote it but it does not work. This integral is very closely related to the sophmores dream that states  $$ \int_0^1 x^{-x}\mathrm{d}x = \sum_{n=1}^\infty n^{-n} = 1.27\ldots $$  For example here   Now I want to bound the integral, and showing that is less that 2.  For the interval $[0,1]$ a good bound is rewriting it to $\exp(x\log x)$ and using the expansion   $$ 1 - x \log(x) + \frac12 (-x \log(x))^2$$  but how does one handle $[1,\infty)$ ? In this answer here     gives bounds to the integral, but they are not tight enough.. So to taste my question again, how does one prove that   $$ \int_0^\infty \frac{\mathrm{d}x}{x^x} \leq 2 $$ Having recently introduced an overload of a method the application started to fail. Finally tracking it down, the new method is being called where I did not expect it to be.  We had  setValue( const std::wstring&amp; name, const std::wstring&amp; value );  std::wstring avalue( func() ); setValue( L"string", avalue ); std::wstring bvalue( func2() ? L"true", L"false" ); setValue( L"bool", bvalue ); setValue( L"empty", L"" );   It was changed so that when a bool value is stored we use the same strings (internal data storage of strings)  setValue( const std::wstring&amp; name, const std::wstring&amp; value ); setValue( const std::wstring&amp; name, const bool&amp; value );  std::wstring avalue( func() ); setValue( L"string", avalue ); setValue( L"bool", func2() ); setValue( L"empty", L"" ); &lt;&lt; --- this FAILS!?!   The problem with L"" is that it is implicitly casting and previously it was happy to be a std::wstring, but not it prefers to be a bool. The MSVC compiler does not complain, or raise warning, so I'm worried that even if I "fix" the setValue( L"empty", L"" ); to be  setValue( L"empty", std::wstring() );   somebody else may come later and simply use setValue( L"empty", L"" ); and have to track down this issue again.  We thought to use explicit on the method but it is not a valid keyword for this usage. Is there some way to get the compiler to complain about this, or otherwise prevent the issue?  Otherwise I'm thinking to change the name of the method which takes a bool to ensure it can't make an incorrect guess. No sound (speakers/jack) + microphone's dead after spilling water Sadly, yesterday I've spilled some water on my MacBook Pro (El Capitan). Before you yell at me - it was closed, turned off and it wasn't a lot of water, the laptop was wet only on the top and under - not inside.  Today I've turned him on. At first battery wasn't recharging for some reason, but SMC reset fixed the problem.  At the first booting speaker was like talking to me, hard to explain but it was weird. Also only right speaker was "talking", despite the fact that only left side of the laptop was watered. Then there was no sound at all, not from the speakers, nor from the headphones. Also microphone's not working. USB ports are okay. The water was spilled from the left side of the laptop. I know this is hardware issue, and something's broken, but I want to be 100% sure. No it's not muted. I've also tried NVRAM reset a few times, but it doesn't fix the problem :(  There might be one factor, before spilling, my laptop "died" for the first time (battery energy ran off), but I doubt it's the case. (but hey, every info matters, right?)  It wouldn't be weird for me, if only left speaker wouldn't work, but built-in microphone not working is kinda weird in this case, isn't it?  I just want to ask you guys, what else can I check, before I'll be 100% sure it's dead inside?  I've plugged in external microphone - it's not working too. I know that non-married lovers address each other by saying “This is my girlfriend/boyfriend.” I know that married couples address each other by calling “my wife/husband”.  I also know that gay lovers who are not married (yet?) address each other by saying "my boyfriend" (for gays) and "my girlfriend" (for lesbians).  But if they are married, how do they address each other?  And how do we describe them? I mean if they are gays, are they “husband and husband” or “husband and wife” (one of them acts like the wife)? And if they are lesbians, are they “wife and wife” or “husband and wife” (one of them acts as the husband)?  I know they can be referred to as a gay couple or gay lovers from , but I couldn't find the answer to address each of the two. Origin/reason for the expression "on the bus" instead of "in the bus" This is sort of a follow up to my question .  I was told a while ago that the reason why we use "on the bus" instead of "in the bus" is because back in the day buses were open, that is, they didn't have a roof.   Is this story correct or is there another reason why the correct expression is "on the bus", in spite of the fact that when one gets on the bus, he is actually inside the bus? Creating fillable PDFs I'd like to create a LaTeX document that when rendered into PDF, has forms that can be filled out using Adobe Reader or other such programs. Then I'd like to be able to extract the data. I deliberately would like to avoid using Acrobat for all the usual reasons (non-free, need different versions for different platforms etc).   Can this be done ? Let $a,b,c&gt; 0$ be three real numbers such that $a+b+c=1$. I want to prove that   $$\frac{a}{a^2+b^3+c^3}+\frac{b}{b^2+a^3+c^3}+\frac{c}{c^2+a^3+b^3}\le\frac{1}{5abc}.$$  My attempt: Using AM-GM on each denominator gives (here, LHS denotes the left-hand side) $$LHS\le\frac{1}{3a^{\frac12}bc}+\frac{1}{3b^{\frac12}ac}+\frac{1}{3c^{\frac12}ab}.$$  However, I think that my attempt doesn't work because the last expression can get larger than $\frac{1}{5abc}$. In fact, if we multiply with $3abc$ then the original inequality is: $$\sqrt a+\sqrt b+\sqrt c\le\frac35$$  However, as $a,b,c&lt;1$, $$\sqrt a +\sqrt b + \sqrt c&gt; a+b+c=1&gt;\frac35.$$ So my upper bound is always larger than the given one. Extend tourist visa stay in USA due to coronavirus and waive I-539 fee My mom has come to US on a tourist visa and her I-94 expires on the first week of May.   Due to the coronavirus, travel restrictions have been imposed in our home country (India). Also we want to avoid the risk of traveling in flights at this time.  Is there an easy way to to extend her stay in the US by one or two months?  I am aware that we should fill out an  to extend our stay. But in-order to submit the online application it requires a fee of $370.    Is filing I-539 the easiest way to extend her stay at this time? If so, is it possible to waive the fee due to the coronavirus situation?  After filing I-539 should she wait for an approval to continue her stay? Or is the receipt good enough?   Can you please help me with these? Thanks!  [Edit 1]:  With the current situation of the virus, traveling anywhere sounds like a very risky operation, especially for elders.   That is the main reason behind this question. If the US government will allow visitors to overstay until Covid-19 settles down! Stop sound from speakers when connecting headphones I guess this question already had the answer here but I can't find it. I'm using 12.04.  Update:  The problem is that I can hear the sound from my laptop's speakers even if I plugged in my headphones. Headphones is just standard stereo headphones. And the most interesting thing is  that all was working just a week ago.  I tried to play with pulseaudio and alsamixer settings - no results.