Can I take a fully-charged portable phone charger on a plane?
Are battery packs allowed in hand luggage?
What is the intuition behind defining completeness in a statistic as being impossible to form an unbiased estimator of $0$ from it? I'm working on a project using logistic regression to predict student retention. The data were collected through three self-report instruments. We are trying to find out which predictors are powerful enough to predict the at-risk students. I came across some articles saying a balanced sample (50% stay, 50% dropouts) is desirable for such study, e.g. Glynn, J.G., Sauer, P.L., &amp; Miller, T.E. (2003). , NASPA Journal, 41 (1), 41-67:     A problem however, is that the distribution of the dependent variable is likely to be highly skewed toward persistence. For example, if 85% of the analysis sample were persistors, a classification model that classified every student as a persistor would have a success rate of 85%, or would classify 85% of student correctly. To resolve this issue, the maintenance of relative balance between the number of dropouts and the number of persistors (about 50% each) in the analysis sample was desirable.   Is this true? Our sample only has about 25%-30% dropout students. Will this affect the results? Show that function $f$ has a continuous extension to $[a,b]$ iff $f$ is uniformly continuous on $(a,b)$ Let $E \subset F \subset X$ and $f:E\rightarrow Y$. We say that the function $g:F\rightarrow Y$ is an extension of $f$ if $g(x) = f(x)$ for all $x \in E$.   Let $f: (a, b) \rightarrow \mathbb{R}$. Show that $f$ has a continuous extension to $[a, b]$ if and only if $f$ is uniformly continuous on $(a, b)$.   $(X,d)$ is a metric space.  Hint: To prove $\Leftarrow$ start by showing that $f$ maps Cauchy sequences to Cauchy sequences. Then how should you define $g(a)$ and $g(b)$?  The $\Rightarrow$ part of the proof was quite simple, but even with the hint, the other way seems a bit difficult. Doesn't the first part of the "hint" follow from the way we defined $f$? If so, how do I prove this? Help/Hints appreciated! A word with a wide range of meanings Is there a better alternative to ambiguous for a word with a wide range of meanings, difficult to find, because they become different in connection with person's opinion. Evaluate the integral $\int_0^\infty \frac{dx}{\sqrt{(x^3+a^3)(x^3+b^3)}}$ Turning DisplayPort monitor off disables monitor completely I have 2 monitors connected to a NVIDIA GeForce GTX 660:   Left is 1920x1080 via DVI (Samsung SyncMaster 2443BW) Right is 2560x1440 via DisplayPort and is set to Primary (Samsung SyncMaster SA850)   I often leave my computer running overnight (working on long render job, doing backups, etc) so I only power off my monitors manually. However, if I power off the primary monitor, it is disabled completely as if it were unplugged from the graphics card (i.e. icons are moved, open apps are moved and resized to fit on the new primary monitor). If I switch from DP to a DVI cable, this does not occur. It seems to be an issue when using DisplayPort.  Is there a way to disable the monitor from being disabled completely in Windows when I power it off physically?   I have found no relevant settings in either Windows Display settings, nor the NVIDIA control panel software.  Edit #1: I'm using an .  Edit #2: Here is a screenshot of my NVIDIA Control Panel v7.2.710.0:   Edit #3: Here are screenshots of my Monitor configuration:    Clicking on Advanced settings reveals a Generic PnP monitor running at 59 Hz? 60 Hz is the only other option available.    Here is my secondary monitor which is connected via DVI:    Edit #4: If I open the "Screen Resolution" configuration panel and power the monitor off (via the power switch), this is what is shown:    It looks like I disconnected the monitor from the video card. This is a neat little problem that I was discussing today with my lab group out at lunch. Not particularly difficult but interesting implications nonetheless  Imagine there are a 100 people in line to board a plane that seats 100. The first person in line realizes he lost his boarding pass so when he boards he decides to take a random seat instead. Every person that boards the plane after him will either take their "proper" seat, or if that seat is taken, a random seat instead.  Question: What is the probability that the last person that boards will end up in his/her proper seat.  Moreover, and this is the part I'm still pondering about. Can you think of a physical system that would follow this combinatorial statistics? Maybe a spin wave function in a crystal etc... System App Permissions I have an application that needs root permissions to run.  No biggie, all of my personal devices are rooted, so I am very comfortable with the process. The problem is that this application is to be used on company owned devices issued to certain employees and I don't want them to be able to uninstall the application nor do I want them having root access to the device.  I was thinking that the following process would accomplish my goals:   Root the device Install my app as a system app Launch the application and grant su rights to it Unroot the device   Since it would be a system app, and the device wouldn't be rooted, users would be prevented from removing the app.  What I am unsure of is whether or not that application would retain its root privileges once the device is unrooted?   Any feedback or insight would be greatly appreciated! I dual booted ubuntu 11.04/11.10 a while ago with a USB stick and i want to uninstall it.   I would like to completely uninstall the old version and get 12.04.  I have a 64 bit laptop. Please help! If you activated a free upgrade to Windows 10 or bought and activated   Windows 10 from the Microsoft Store, you have a digital license for   your device. This means you can reinstall the same edition of Windows   10 that your device has a digital license for without entering a   product key. During reinstallation, if you’re asked to enter a product   key, you can skip this step. Windows 10 will automatically activate   online after the installation is complete.   source:   Does MS digital license 'fingerprint' hardware information  during the free upgrade / activation and store it (at Microsoft) , so that the next re-install queries MS for the fingerprint and activates Windows 10?  Thought the disk drive may change, I expect that none of the other fingerprinted hardware will change. I know that one can use "they" / "them" / "their" in place of "he" / "him" / "his" or "she" / "her" / "hers" when the subject's / direct object's gender is not known; for instance, just looking at the default user's about me section on Stack Exchange sites:     Apparently, this user prefers to keep an air of mystery about them   My question is what happens when someone wants to reference the subject using a pronoun instead.  Should the verb be conjugated accordingly to the pronoun? E.g.:     Apparently, they prefer to keep an air of mystery about them   Or should the conjugation be retained? E.g.:     Apparently, they prefers to keep an air of mystery about them   The former looks unclear because it wouldn't allow the reader / listener to understand if the writer / speaker is talking about a single person or about a group of people, however the latter sounds very weird, at least just to the non-native speaker which I am. Functions satisfying $f\left( f(x)^2+f(y) \right)=xf(x)+y$ Removing Ubuntu from UEFI Bios Menu So my friend has a USB flash drive that isn't working. I don't know a whole lot about "recovery" software so I figured I'd ask you guys.  What steps can I try (I have access to a Linux machine as well) to see....if I can get ANYTHING off the flash drive?  I've google'd around, but most of the stuff seems for windows. Permission Subscribe to Dashboards: Add Recipients depends on permission(s): Subscribe to Dashboards How to manage and restore a modern iPhone or iDevice on ubuntu with iTunes This question—how to install iTunes on ubuntu—has been asked many times before on this site, but the answers are all outdated and involve Wine or some other tool that no longer works for the most recent version of iTunes. Put simply, I need to regularly back up and occasionally restore the firmware on an iPhone 6.   I cannot:   dual boot Windows—for some reason installing one OS makes the other unbootable &amp; after days of headache &amp; dozens of reinstalls I’ve decided to just leave Ubuntu be &amp; not try to preserve Windows. Plus “just use Windows” is not really a solution on an Ubuntu forum. use libimobiledevice-dev. libimobiledevice-dev doesn’t let you manage iOS updates or sync music anymore. Buy another phone. This one should be obvious but for some reason some asshat always comments “too bad lmao shouldntve bought an iphone ;P”. Let $f: \mathbb R^2 \to \mathbb R$ defined as   $f(x,y)=(x^2+y^2)\sin(\dfrac{1}{\sqrt{x^2+y^2}})$ if $(x,y) \neq (0,0)$, $f(x,y)=(0,0)$ if $(x,y)=(0,0)$  Prove that $f$ is differentiable at $(0,0)$ but that the partial derivatives of $f$ are not continuous at the origin.  The attempt at a solution:  I had some problems at the first part of the exercise:  I've calculated $\dfrac{\partial f}{\partial x}(0,0)$ and $\dfrac{\partial f}{\partial y}(0,0)$, both exist and are equal to $1$.  So, to prove $f$ is differentiable at the origin, I have to show that   $\lim_{(x,y) \to (0,0)} \dfrac{|f(x,y)-(f(0,0)+&lt;\nabla f(0,0),(x,y)&gt;)|}{\|(x,y)\|}=0$ But $\lim_{(x,y) \to (0,0)} \dfrac{|f(x,y)-(f(0,0)+&lt;\nabla f(0,0),(x,y)&gt;)|}{\|(x,y)\|}$ equals  $\lim_{(x,y) \to (0,0)} \dfrac{|(x^2+y^2)\sin(\dfrac{1}{\sqrt{x^2+y^2}})-(x+y)|}{\|(x,y)\|}$. I don't know how to show this limit equals $0$.  For the second part (I've only analyzed $\dfrac{\partial f}{\partial x}$ since both cases are the same), what I did was try to show that $\lim_{(x,y) \to (0,0)} \dfrac{\partial f}{\partial x}(x,y) \neq \dfrac{\partial f}{\partial x}(0,0)$   I thought of considering the curve $\phi(t)=(t,0)$, so   $\lim_{t \to 0} (f\circ \phi)(t)=\lim_{t \to 0} 2t\sin(|t|^{-1})-\dfrac{t\cos(|t|^{-1})}{|t|^{-1}}$. But $\lim_{t \to 0^{+}} \dfrac{t\cos(|t|^{-1})}{|t|^{-1}}=\lim_{t \to 0^{+}} \cos(\dfrac{1}{t})$ and this limit doesn't exist, so the original limit doesn't exist. This shows the partial derivative with respect to $x$ at the point $(0,0)$ is not continuous.   I would appreciate if someone could help me to finish the first part and tell me if what I did in the second part of the problem is correct. character "5" repeated in text fields, and system freezes I am running Ubuntu 15.10, with the latest updates.  When I type in a text field (google search, type name of file, etc..) the number 5 gets typed on its own and it keeps repeating until I press ESC and when I try to continue typing the number 5 resumes filling in the text field.  I have tried to set the keyboard repeat to zero, but does not help.  This does not happen all the time, sometimes if I shut down the computer it then behaves normally when I restart it, other times the computer becomes useless because I cannot type in any of the text fields.  Thanks Sal Fire (at, on, in, to) target How to correctly choose the preposition in "fire (at, on, in, to) target"? Which Distribution Does the Data Point Belong to?