From the research I've done the common answer is that you can not remove insignificant dummy variables from a regression. I'm having a hard time finding academic papers or books that back up this thought. If anyone knows of any papers dealing with this issue or a good place to search through statistics papers that would be great!
After seeking clarification about linear model coefficients  I have a follow up question concerning non-signficant (high p value) for coefficients of factor levels.  Example: If my linear model includes a factor with 10 levels, and only 3 of those levels have significant p values associated with them, when using the model to predict Y can I choose to not include the coefficient term if the subject falls in one of the non-signficant level?  More drastically, would it be wrong to lump the 7 non-significant levels into one level and re-analyze?
What is the difference between char * const and const char *? Why does this Excel file keep asking to save? For my MAC laptop, I only have 250GB and out of this 250GB MAC is taking up 129GB in the other section. I looked everywhere to the best of my knowledge. Please note my home directories is only 45GB. Can you somehow please help me? Is there an infinite amount of wavelengths of light? Is the EM spectrum continuous? The electromagnetic spectrum is a continuum of wavelengths of light, and we have labels for some ranges of these and numerical measurements for many.  Question: Is the EM spectrum continuous such that between two given wavelengths (e.g. 200nm and 201nm) there is an infinite number of distincts wavelengths of light?  Or is there some cut-off of precision with which light might exist (e.g. can light only have wavelengths of whole number when measured in nanometers, etc.)? "She need not worry" or "she needs to not worry"? I just came across this weird use of &quot;need not&quot; on :  Madam/sir, My daughter is stuck in Uk . She has lost her  . She is difficult to return back India home [sic]. Please help  In response,  says:  She need not worry. She should stay where she is. Just tell her to keep herself safe. Please delete your tweet.  Shouldn't it be &quot;she doesn't need to worry&quot; or &quot;she needs to not worry&quot; given that the subject is &quot;she&quot; (singular)? Or is this some kind of grammatical construction I don't know? I believe who wrote it was a native speaker of English and they might be correct. Can someone explain this please? How do I find slimes in Minecraft? In early alpha I remember Minecraft videos showing slimes deep underground. I think you would attack them then they split into several smaller slimes. But I've never found a slime for myself. In what conditions can you find slimes? Are they definitely still in Minecraft? $dx$ appears in differential equations, such us derivatives and integrals.  For example, a function $f(x)$ its first derivative is $\dfrac{d}{dx}f(x)$ and its integral $\displaystyle\int f(x)dx$. But I don't really understand what $dx$ is. How do you tell if caps lock is on using JavaScript?  One caveat though: I did google it and the best solution I could find was to attach an onkeypress event to every input, then check each time if the letter pressed was uppercase, and if it was, then check if shift was also held down. If it wasn't, therefore caps lock must be on. This feels really dirty and just... wasteful - surely there's a better way than this? Does the MacBook battery cycle count reset when replacing a battery I've been  on battery cycle counts and checked out my current count on my MacBook (13-inch, Aluminum, Late 2008) - recommended maximum cycle count is 500.  I've had this laptop now for over 4 years and at the 2 year mark I had the battery replaced by AppleCare. The first time I checked out the cycle count was today and it's currently on 1004. Now my question is, is this the cycle count of the battery since I replaced it (as in, it reads the cycle count from the battery), or is it the combined cycle count (as in, it stores the count somewhere and increments occasionally)? My assumption is that it's the count of that battery but I have no idea how to verify this.  Either way, it looks like I need a new battery ;) multiplicative group of infinite fields A pseudometric on the space of the measurable functions is complete How many numbers are in the Fibonacci sequence below a given threshold? Assuming I'm asked to generate Fibonacci numbers up to N, how many numbers will I generate? I'm looking for the count of Fibonacci numbers up to N, not the Nth number.  So, as an example, if I generate Fibonacci numbers up to 25, I will generate:   1, 1, 2, 3, 5, 8, 13, 21 that's 8 numbers   How do I calculate this mathematically for an arbitrary "n"? Gay rights – does Star Trek ever address this issue? I am aware of the picture of the man wearing the 'dress' from TNG, which promotes gender equality, but are gay rights ever addressed in Star Trek at all? (All seasons accepted.) Reordering polygon shapefile permanently? Terminating Python scripts in Processing framework I'm writing a Python script to use it in Processing framework. I need to cancel script execution if certain conditions are met (to save user's time). I tried to use sys.exit(arguments) command. The issue is that not only the script, but QGIS itself shuts down too. I also tried quit() but result is the same. How should I terminate script in Processing framework? The following code is for reproduction purpose only. I don't need ad hoc solution for this particular case because I already have it. I need to know how to deal with this issue in general. ##Raster processing=group ##raster_1=raster ##raster_2=raster   from osgeo import gdal import sys from numpy import * import ntpath import re import platform from PyQt4 import QtGui   raster_1 = gdal.Open(raster_1) raster_2 = gdal.Open(raster_2)  rasters_list = [raster_1, raster_2]  # create a message for the case when CRSs of rasters do not match class WrongCRS(QtGui.QMessageBox):    def __init__(self):     super(WrongCRS, self).__init__()      self.initUI()    def initUI(self):      self.warning(self, 'Oops!',             &quot;Rasters must have the same CRS!\n\nExecution cancelled!&quot;, QtGui.QMessageBox.Ok)  # check CRS proj = None for raster in rasters_list:   new_proj = raster.GetProjection()   if proj is None:     proj = new_proj   else:     if proj != new_proj:       WrongCRS()       sys.exit('CRSs do not match!')     else:       continue Removing non numeric characters from a string $\newcommand{\P}{\mathbb{P}}$Is it valid to interpret $\P(B|A)$ as "infinite probability" when $\P(A) = 0$? How can we prove that for every pair $N \in \mathbb{N}$, and natural number $\beta\in [2, \infty)$ there exists a unique set of integers $x_i \in [0, \beta -1]$, $k\in [0,\infty)$ such that:  $$N = \sum_{i=0}^{k}\beta^ix_{i}, \quad $$  It's a question if every positive integer has its unique representation in every base $\beta$. Is the validity of above statement somehow related to Horner's rule? Java process memory check test Is there some way to get explorer to generate thumbnails without actually having to navigate and scroll through every folder?  All I could get was a command prompt script that would load an explorer window for all subfolders, however only images that were visible would have thumbnails created.