Social science PhD student here looking for a little help.   I set out to collect around 300 online surveys for a study, but ended up with over 4,000. At that sample size should I sub-sample my results because it's more likely that significant results will be found because of the sample size?  Thanks.
In a  of Amstat News, the authors (Mark van der Laan and Sherri Rose) stated that "We know that for large enough sample sizes, every study—including ones in which the null hypothesis of no effect is true — will declare a statistically significant effect.".  Well, I for one didn't know that. Is this true? Does it mean that hypothesis testing is worthless for large data sets?
Why does Skynet take prisoners? In the Terminator franchise, extermination camps are often mentioned. But from a machine-logic POV, wouldn't it make more sense to just kill all humans on sight, period? Or herd them into small areas and nuke them? (even today's military electronics are hardened against EMPs and Skynet wouldn't care about the environment.)   IIRC, the reasoning behind ghettoization / concentration camps / extermination camps / gas "showers" is to misdirect or mislead people both inside and outside the country as to what was really going on. But Skynet doesn't have to worry about bad publicity, and can manufacture all the free labor it needs. Is there any in-universe explanation for keeping large groups prisoners? What inspired Tauriel's story arc? I know Tauriel is a Jackson created character, but I wondered if anywhere in the legendarium there was fodder for the story arc between her and Kili.  I do not have access to all my books for the time being and recall stories of love between men and elves in the Silmarillion and Appendices but don't remember any such stories between elves and dwarves and wondered if there was any basis of inspiration for this aspect of their relationship within Tolkien's works.   This movie, of course, departs even further from the original than those made before it, but as a story unto itself, I can still appreciate the ride, so if there is no Tolkien basis, what inspired Jackson, Boyens, and Walsh to create this particular arc?  Is there interview info or anything? Midpoint-Convex and Continuous Implies Convex Can I use Wilcoxon Signed-Rank Test to test pairs of data in a time series? I have a dataset of measurements (non-normally distributed). Each line of this dataset is composed of two measurements of the same variable at a specific time (i.e. XYY [time, meas1, meas2]). This dataset contains 24 lines.  Is it correct to use the Wilcoxon Signed-Rank Test to compare these two measurements? Is it correct to use this test to compare the mean value of these measurements between different experiments?  Thanks Mismatch Reputation in the thumbnail and the actual Reputation Actually this was quite surprising. A casual troll in the Users Page revealed few users with negative vote. One example is here    Then trying to see what could have causes such a low reputation, I peeked inside the Profile Page of this particular User and was surprised to see a decent positive score.    Can someone explain to me how this can be possible? How do I integrate Github files to Orange for ML? I am currently trying to make a facial recognition workflow with Orange but since the widgets are still prototypes they are not all available in Orange. I found the Github files for the widgets but don't know how to install this so that I can see and use the widgets in Orange. Displaying world country shapefiles centered on Pacific Ocean using Robinson or Miller Cylindrical projection in QGIS? I wish to display a map in QGIS (world country shapefiles) showing all countries but centered on the Pacific area.   I am not familiar with Proj4, so is there any way this can be done in QGIS? Proving a sequence defined by a recurrence relation converges How can I prove that this iterative sequence converges to $2$? Can I use the convergence definition?  $$a_{n+1} = \frac{a_n}{2} + \frac{2}{a_n},\qquad  a_0 = 4  $$  Thanks for the help. Proving that the Intersection of any Collection of Compact Sets is Compact I was trying to do this problem this way:  Let $\mathcal{B}=\{B_i\}$ be a collection of compact sets. By Heine-Borel, each of the $B_i$'s are closed and bounded. We already know that the intersection of a collection of closed sets is once again closed, so $\cap \mathcal{B}$ is closed.  If I can prove $\cap\mathcal{B}$ is bounded as well, I can use Heine-Borel to say it is compact. So I was not sure how to show it was bounded, but a friend showed me his way of doing it. He did it the following way:  Let $b,a\in\mathbb{R}$ be an upper and lower bound for $B_1$, respectively. Since $\cap\mathcal{B}\subset B_1, a$ is a lower bound for $\cap \mathcal{B}$ and $b$ is an upper bound for $\cap\mathcal{B}$. Therefore, $\cap\mathcal{B}$ is bounded and then by Heine-Borel, it is compact.  My question is on the paragraph right above. I don't understand why what he did means that $a$ and $b$ are lower and upper bounds for $\cap\mathcal{B}.$ Can anyone explain why this is? Thanks. Does the 90 days VWP rule expire if you travel from the US to Canada? I'm on a New Zealand passport.  From most US Embassy webpages:     The Visa Waiver Program (VWP) enables nationals of certain countries,   including Australia, New Zealand, and the U.K., to travel to the   United States for tourism or business for stays of 90 days or less   without obtaining a visa, if certain requirements are met. Under the   VWP, time spent in Canada, Mexico, and adjacent islands counts towards   the maximum of 90 days stay allowed under the program.   I'll be there on a 1-year working holiday visa starting when I arrive in Vancouver. I'm spending 3 days in Hawaii en route to Vancouver. This seems to imply that 90 days after landing in Hawaii, my time will be up and I won't be able to get back into the US, as my living in Canada will not reset the clock. What if after this time I want to say, pop across the border to Seattle? How can I restart the 90 days, without having to resort to say, flying to Japan and back just to reset it? Avoid linebreaks in LaTeX console / log output (or increase columns in terminal) Is it possible to tell the LaTeX command not to use line breaks in its console / log output?  This would make it easier to automate the processing of the log file, e.g. extracting the names of missing graphics files like in this output  ! LaTeX Error: File `figures/triggers/muontriggers/notmu18_medium_mu10_loose/2d map_abs_eta_phi.pdf' not found.   which are otherwise cut into pieces and unnecessarily difficult to grep etc. Memory management in Objective-C Why does find -mtime +1 only return files older than 2 days? I'm struggling to wrap my mind around why the find interprets file modification times the way it does.  Specifically, I don't understand why the -mtime +1 doesn't show files less than 48 hours old.   As an example test I created three test files with different modified dates:   [root@foobox findtest]# ls -l total 0 -rw-r--r-- 1 root root 0 Sep 25 08:44 foo1 -rw-r--r-- 1 root root 0 Sep 24 08:14 foo2 -rw-r--r-- 1 root root 0 Sep 23 08:14 foo3   I then ran find with the -mtime +1 switch and got the following output:  [root@foobox findtest]# find -mtime +1 ./foo3   I then ran find with the -mmin +1440 and got the following output:   [root@foobox findtest]# find -mmin +1440 ./foo3 ./foo2   As per the man page for find, I understand that this is expected behavior:   -mtime n         File’s  data was last modified n*24 hours ago.  See the comments         for -atime to understand how rounding affects the interpretation         of file modification times.   -atime n        File  was  last  accessed n*24 hours ago.  When find figures out        how many 24-hour periods ago the file  was  last  accessed,  any        fractional part is ignored, so to match -atime +1, a file has to        have been accessed at least two days ago.   This still doesn't make sense to me though.  So if a file is 1 day, 23 hours, 59 minutes, and 59 seconds old, find -mtime +1 ignores all that and just treats it like it's 1 day, 0 hours, 0 minutes, and 0 seconds old?  In which case, it's not technically older that 1 day and ignored?   Does... not... compute. What is a magic number, and why is it bad? Cloth collision with an object When to use Stateful session bean over Stateless session bean? Create JSON using apex Most properties of a single binary operation can be easily read of from the operation's table. For example, given $$\begin{array}{c|ccccc} \cdot &amp; a &amp; b &amp; c &amp; d &amp; e\\\hline a     &amp; e &amp; d &amp; b &amp; a &amp; c\\ b     &amp; d &amp; c &amp; e &amp; b &amp; a\\ c     &amp; b &amp; e &amp; a &amp; c &amp; d\\ d     &amp; a &amp; b &amp; c &amp; d &amp; e\\ e     &amp; c &amp; a &amp; d &amp; e &amp; b \end{array}$$ it is easy to check that it is closed (no elements occur in the table which don't occur as row or column index), commutative (the table is symmetric), has a neutral element (the row and column of $d$ are copies of the index row/column), and has an inverse element for each element (there's a $d$ in each row and column). In other words, almost all important properties can immediately be seen. The only part missing is associativity.  Therefore my question: Is there a simple way to see directly from the operation's table (i.e. without doing explicitly all the calculations) if an operation is associative? List of blogs to learn more about Ubuntu Add blogs and websites that are useful in the quest to know/learn more about Ubuntu.  One blog per answer, please - you can vote answers up/down as you feel appropriate. If you feel the blog is biased towards or is good for particular tasks, please mention them. Schengen refusal formulae can be difficult to understand sometimes.    When an applicant receives a refusal with "Justification for the purpose and conditions of the intended stay was not provided", what does it mean?