In my analysis section where I used a partial least squares (PLS) structural equation technique, A reviewer commented that: "Not controlling for state or university etc, particularly in a diverse country like Nigeria, is a serious limitation in the quantitative analysis"  What did he mean, and any possible solutions, please? Thank you
To my understanding, "Control" can have two meanings in statistics.   Control group: In an experiment, no treatment is given to the member of the control group.  Ex: Placebo vs Drug: You give drugs to one group and not to the other (control),  which is also referred as "controlled experiment".  Control for a variable: Technique of separating out the effect of a particular independent variable. Some of the other names given to this techniques are, " accounting for", "holding constant", "controlling for", some variable.  For example: In a Football viewing study (like or not like),  you may want to take out the effect of gender as we think gender causes bias, that is, male may like it more than female.     So, my question is for point (2). Two questions:  How do you "control"/ "account for" variables, in general. What techniques are used? (In terms of regression, ANOVA framework).   In above example, does choosing male and female randomly constitutes control? That is, is "randomness" one of the techniques for controlling other effects?
Is there a word or phrase for two nouns or adjectives joined by a conjunction (usually "and") in a fixed sequence?        alive and well           fast and furious   hat and gloves   pen and pencil   law and order   wit and wisdom   salt and pepper   bacon and eggs   horse and carriage   Adam and Eve   ladies and gentlemen   loud and clear   heads or tails   yes or no   dead or alive How can light be called electromagnetic if it doesn't appear to be electric nor magnetic?  If I go out to the sunlight, magnets aren't affected (or don't seem to be).  And there is no transfer of electric charge/electrons (as there is in AC/DC current in space).   In particular, the  (which light is supposed to be composed of) have no electric charge (nor do they have ).   I'm looking for an explanation that can be appreciated by the average non-physicist Joe. Does Java have buffer overflows? Does Java have buffer overflows? If yes can you give me scenarios? Differences in the behaviour of pinching a garden hose and closing a tap Let's say you have a garden hose connected to an ordinary water tap which is opened fully. If you pinch the end of the hose, water leaves the hose at a higher speed (and this can be useful while watering plants, to reach pots which are further away). However when a tap (with no hose connected) is opened only slightly, water flows out at a low speed, possibly even in drops.  The actions of pinching the end of a hose and of almost-closing an open tap seem similar, so why the difference in behaviour? I recently saw a question titled "" (10k+ users only). I thought, "surely someone has asked this question before", and began looking for a duplicate.  is a question with the exact same title, just with a little different punctuation and casing. It was "Jquery vs Javascript" and "jQuery vs. Javascript?". The only difference being the ., ?, and the casing.  Since we now , I propose that when checking for questions with duplicate names, certain punctuation be striped out to prevent the duplicate from occurring in the first place.  As pointed out in the comments, if isn't already, white-space and non-printable characters may want to be removed for duplicate detection as well. Is the function $\mbox{tr}(XAX')$ convex? Is the function $\mbox{tr}(XAX')$ convex, where $A$ is a positive semidefinite (PSD) matrix? I know that for a general $A$, the above trace function is not convex. But for a PSD $A$, is the function convex? error with inner class object If a superconductor has zero resistance, does it have infinite amperage? A generalization for Serret's integral $\int_0^a \frac{\ln(1+ax)}{1+x^2}dx$ Is a noisy laptop fan caused by dirt on the fan? I know you can select a tag and then click on unanswered to view the unanswered questions for that tag.  But is there a way to view questions only for a certain set of tags > 1 tag?  Mainly I'd like the union of tag1 with tag2 with tag3 with tag4. But also the intersection of tags would be nice as well. El Captain update download doesn't continue after restarting the Mac I started to download the El Capitan upgrade, but then I shut down my computer. The day after I wanted to continue the download but in App Store it shows "Waiting..." and doesn't do anything. Also when I go to the updates section, it shows the button "Download" but it's inactive. Maybe someone can help me? I tried to find the download file in some directory to delete it and start over but I couldn't find it. Simple past or present perfect? Which is preferable, simple past or present perfect, in situations like this one: I had a conversation with my friend and we planned to do something; shortly afterwards I call him back to announce the accomplishments. My biggest doubt about simple past is that perfect aspect is used to indicate past action (accomplishment) with current relevance, at the same time I'm not sure if I'm allowed to use present perfect, because there's a gap between accomplishing and the current moment, which is a characteristic of simple past. I am trying to prove the following by Mathematical Induction:  $$\sum_{i=1}^n i\cdot i! = (n+1)!-1\quad\text{for all integers $n\ge 1$}$$   My proof by Induction follows: First prove $P(1)$ is true,  $$\sum_{i=1}^1 i\cdot i! = (1+1)! - 1$$  Then, for all integers $k &gt;= 1$, if $P(k)$ is true then $P(k+1)$ is also true,  $$ \sum_{i=1}^k i\cdot i! = (k+1)! - 1$$ Then, we must show that $P(k+1)$ is true   $$ \sum_{i=1}^{k+1} i\cdot i! = ((k+1)+1)! - 1\\ \sum_{i=1}^{k+1} i\cdot i! = (k+2)! - 1$$  I am currently struggling with the next step to show that $P(k)$ is equal to $P(k+1)$. How would I finish this prove by induction? Background:   Story: A colleague of mine told me about  and it seems good to me. I am always trying to use tools which Mac OS X itself gives me, so I've given the Keychain a try. It seems satisfying, but I don't know how to tell Google Chrome to use my specific keychain. I need it to separate saved stuff for work and for private (syncing private to work, but separated from work data).  Stuff:   Google Chrome 21.0.1180.57 (Fully updated) Mac OS X Lion (Fully updated) OS X Mountain Lion (Fully updated)   Question:  How do I tell to Chrome to use a specific keychain and to save data from/to this keychain? There is a sentence:     No sooner had he sat down than he fell asleep.   I just do not understand, is this an inversion? And if so, I still do not understand the sentence. Multiple workspaces on Ubuntu 18.04.1 LTS and later with GNOME Shell Any idea how to have more than 2 workspaces on Ubuntu 18.04.1? Is there a measurable set $A$ such that $m(A \cap B) = \frac12 m(B)$ for every open set $B$? Is there a measurable set $A$ such that $m(A \cap B)= \frac12 m(B)$ for every open set $B$?  Edit: (t.b.) See also  for further answers. Should the noun after "any" be singular or plural? I always thought with "any" I should use the plural, but on the internet I can find both:   It can be found in any book. It can be found in any books Do you have any books? It can be said in any language.  This can be understood by anyone.  It has been used in any form.   So, what's correct?  Is there any rule? Sending an E-mail to all addresses of all contacts in a contact group in Gmail I'm trying to send an E-mail message using Gmail to a contact group where some of the contacts have more than one E-mail address and I want to send the mail to all of them.   Is there a way for me to do that?