I have a confusion in multiple regression about dummy variable trap, so far I had seen tutorials explaining about dummy variable trap and multicollinearity but I'm unable to understand it fully.
What is an example of perfect collinearity in terms of the design matrix $X$?  I would like an example where $\hat \beta =  (X'X)^{-1}X'Y$ can't be estimated because $(X'X)$ is not invertible.
The website I'm working is allegedly going to have a massive hit rate soon after launch. The client is talking about the possibility  of around 2500 hits per second over a day or so.   Ignoring the fact that this hit rate is probably wild client optimism and apart from getting the largest servers possible, what is the best way that Drupal should be configured to support a large hit rate.  I've read Scaling the , ,  and many other pages, but what I'm looking for is real experience of doing this, what works, what doesn't, and what to expect. WordPress twenty eleven sidebar on Pages I am using 2011 theme, any how I managed to get sidebar on single.php pages by installing child theme,  But now I want sidebar on pages,  How do I get it? What book features people living in a tree who move up it in a bubble? Is there a picture showing all the lengths used in lists? Prove that $p \in \mathbb{R}[x]$ can be represented as a sum of squares of polynomials from $\mathbb{R}[x]$ How can i find the python triggered by the GUI? my email limit is exceeded after sending 10-12 emails..what could be the problem..as i have seen the limit is 1000 emails/day.i am not able to find out what could be the problem..Can some give me some suggestions. As i also know we can send 10 emails in a single transaction.I am sending emails in a batch class.  I am calling this batch class on button click and filling emailList with emailsId's.                      String query='Select id from Lead';//No use of this query                     Batch_send_emails bse=new Batch_send_emails();                     bse.query=query;                                                         bse.resendEmails=emailList;                     database.executebatch(bse);           **Batch Class**           if(!resendEmails.isEmpty())           {               for(String s:resendEmails)                {                   emailsLeads.add(s);                }           }           Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();         mail.setToAddresses(emailsLeads);        // mail.setCcAddresses(ccAddresses);         String subject='GoToMeeting Invitation Details for '+subject;         String body='test';          mail.setHtmlBody(body);          mail.setSubject(subject);         Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });          } Improve the editing flow with predefined options for "Edit Summary" Capitalization for a bullet list We walk or ride on our vehicles to our destinations daily. Does our movement have any effect on the rotation of the earth according to Newton's law? What will be the effect if we move all the peoples along with their vehicles at their maximum velocity in one line in one direction along the equator? How much effect will it make? Why doesn't this division work in Python? I checked my  to see whether I can find something similar to the main-site flag-history for chat-flags, but didn't find anything. I recently had the (dis)pleasure of regularly having to deal with a user, that has been deleted multiple times. Whenever they show up (with the same nick-name) again I have to flag them again. I'd like to get an overview of how often I had to do that, and whether my flags were helpful for the moderators. As such I propose the implementation of a flag-history as it is already in place for the main-site for chat-flags, that request moderator intervention. To be completely clear I am not talking about the 10k user flags, which are acted on in a matter of sometimes seconds with instantly visible results, but about moderator attention flags from this menu: Copy over ssh and execute commands in one session Filter bibliography by author? I would like to create a template for a publication list that can then be used by several people. The idea is that there is one bib-file which contains all of the publications. Peer-reviewed entries are marked with the keyword = pr. Then there is the master-file of the type scriptreport in which everyone can integrate their chapter-file in order to merge the publication lists of everybody into one file. The chapter file is the core of everything and should be reusable. It should filter out the entries for the respective author from the bib file and print them out in two lists (peer-reviewed and non-peer-reviewed). My problem is that I don't really know how to filter by author in this case. Here are the rough codes of the two files: Master: \documentclass[a4paper]{scrreprt}  \usepackage{biblatex}  \title{Publication list}  \addbibresource{sample.bib}  \begin{document}     \maketitle          \tableofcontents     \newpage          \include{Researcher}     \newpage \end{document}  chapter: \chapter*{Researcher} \addcontentsline{toc}{chapter}{Researcher}          \nocite{*}     \printbibliography[keyword={pr}, title={Peer-reviewed}]          \nocite{*}     \printbibliography[notkeyword={pr}, title={Non-peer-reviewed}] "Scaled $L^p$ norm" and geometric mean Identical coefficients estimated in Poisson vs Quasi-Poisson model What does the '=>' syntax in C# mean? I just came over this syntax in some of the questions in this forum, but Google and any other searchengine tends to block out anything but letters and number in the search so it is impossible to search out "=>".  So can anyone tell me what it is and how it is used? How to resolve a Java Rounding Double issue Seems like the subtraction is triggering some kind of issue and the resulting value is wrong.  double tempCommission = targetPremium.doubleValue()*rate.doubleValue()/100d;   78.75 = 787.5 * 10.0/100d  double netToCompany = targetPremium.doubleValue() - tempCommission;   708.75 = 787.5 - 78.75  double dCommission = request.getPremium().doubleValue() - netToCompany;   877.8499999999999 = 1586.6 - 708.75  The resulting expected value would be 877.85.  What should be done to ensure the correct calculation? Let $G$ be a graph of minimum degree $k&gt;1$. Show that $G$ has a cycle of length at least $k+1$.  How would I show this? I understand that a cycle is a sequence of non-repeated vertices and the degree of a graph is the number of neighbors the vertex has. When do you use Java's @Override annotation and why? What are the best practices for using Java's @Override annotation and why?     It seems like it would be overkill to mark every single overridden method with the @Override annotation.   Are there certain programming situations that call for using the @Override and others that should never use the @Override?