<?xml version="1.0" encoding="utf-8"?><!DOCTYPE article  PUBLIC '-//OASIS//DTD DocBook XML V4.4//EN'  'http://www.docbook.org/xml/4.4/docbookx.dtd'><article><articleinfo><title>FAQ/regFAQ</title><revhistory><revision><revnumber>86</revnumber><date>2017-07-18 14:22:57</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>85</revnumber><date>2017-02-07 11:54:03</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>84</revnumber><date>2016-03-17 12:29:19</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>83</revnumber><date>2016-02-26 11:06:41</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>82</revnumber><date>2016-01-29 11:05:27</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>81</revnumber><date>2014-09-30 10:26:02</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>80</revnumber><date>2014-09-30 10:25:34</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>79</revnumber><date>2014-09-30 10:25:13</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>78</revnumber><date>2014-06-17 15:27:56</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>77</revnumber><date>2014-04-08 11:14:38</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>76</revnumber><date>2014-04-01 10:17:25</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>75</revnumber><date>2014-04-01 10:05:24</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>74</revnumber><date>2014-04-01 10:01:45</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>73</revnumber><date>2014-04-01 10:00:24</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>72</revnumber><date>2014-04-01 09:59:56</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>71</revnumber><date>2014-04-01 09:59:40</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>70</revnumber><date>2013-03-08 10:17:26</date><authorinitials>localhost</authorinitials><revremark>converted to 1.6 markup</revremark></revision><revision><revnumber>69</revnumber><date>2012-07-10 15:00:50</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>68</revnumber><date>2012-07-10 09:25:44</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>67</revnumber><date>2012-07-10 09:10:11</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>66</revnumber><date>2011-11-14 15:15:00</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>65</revnumber><date>2011-11-14 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11:38:00</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>56</revnumber><date>2011-01-19 16:11:00</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>55</revnumber><date>2011-01-19 16:10:20</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>54</revnumber><date>2011-01-19 12:17:52</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>53</revnumber><date>2011-01-19 12:17:37</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>52</revnumber><date>2010-11-19 12:34:26</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>51</revnumber><date>2010-10-13 09:04:48</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>50</revnumber><date>2010-08-20 10:19:21</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>49</revnumber><date>2010-03-15 11:10:50</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>48</revnumber><date>2010-02-18 14:59:28</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>47</revnumber><date>2010-02-18 14:58:53</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>46</revnumber><date>2009-12-09 10:12:44</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>45</revnumber><date>2009-12-01 12:08:16</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>44</revnumber><date>2009-04-24 11:44:36</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>43</revnumber><date>2009-04-24 11:30:04</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>42</revnumber><date>2009-04-24 11:28:51</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>41</revnumber><date>2009-04-24 11:27:30</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>40</revnumber><date>2009-03-26 16:22:24</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>39</revnumber><date>2009-03-26 16:13:07</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>38</revnumber><date>2009-02-02 15:18:48</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>37</revnumber><date>2009-01-29 15:26:04</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>36</revnumber><date>2009-01-29 15:23:54</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>35</revnumber><date>2009-01-29 15:23:41</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>34</revnumber><date>2009-01-29 15:21:09</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>33</revnumber><date>2009-01-28 15:56:08</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>32</revnumber><date>2008-08-13 15:09:54</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>31</revnumber><date>2008-07-04 12:09:31</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>30</revnumber><date>2008-07-04 11:23:32</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>29</revnumber><date>2008-07-04 11:17:53</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>28</revnumber><date>2008-06-24 15:35:53</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>27</revnumber><date>2008-05-27 15:33:58</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>26</revnumber><date>2008-05-09 11:03:08</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>25</revnumber><date>2008-05-09 10:56:05</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>24</revnumber><date>2008-05-01 14:24:21</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>23</revnumber><date>2008-05-01 14:20:39</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>22</revnumber><date>2008-05-01 14:12:13</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>21</revnumber><date>2008-04-22 10:25:12</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>20</revnumber><date>2008-03-18 14:56:10</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>19</revnumber><date>2008-02-13 14:32:34</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>18</revnumber><date>2007-12-06 13:40:40</date><authorinitials>IanNimmoSmith</authorinitials></revision><revision><revnumber>17</revnumber><date>2007-09-26 15:00:43</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>16</revnumber><date>2007-07-20 09:27:39</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>15</revnumber><date>2007-07-20 09:25:53</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>14</revnumber><date>2007-07-17 14:07:32</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>13</revnumber><date>2007-07-10 10:43:44</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>12</revnumber><date>2007-07-10 10:40:32</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>11</revnumber><date>2007-06-19 11:05:28</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>10</revnumber><date>2007-05-31 10:53:31</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>9</revnumber><date>2007-05-31 10:52:40</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>8</revnumber><date>2007-03-06 12:02:36</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>7</revnumber><date>2007-02-27 15:05:31</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>6</revnumber><date>2007-02-27 15:05:13</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>5</revnumber><date>2007-02-20 14:55:31</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>4</revnumber><date>2007-02-12 12:03:06</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>3</revnumber><date>2007-01-25 11:46:41</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>2</revnumber><date>2006-10-19 15:50:13</date><authorinitials>PeterWatson</authorinitials></revision><revision><revnumber>1</revnumber><date>2006-10-03 11:11:34</date><authorinitials>PeterWatson</authorinitials></revision></revhistory></articleinfo><section><title>Questions about linear regression</title><orderedlist numeration="arabic"><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/E#">What does a number containing an 'E' signify?</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/pearson#">What is the relationship between the Pearson correlation and a simple  regression estimate?</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/suppress#">What is the relationship between predictor variable correlations and the presence of a suppressor variable?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/studentres#">How do I check for outliers in a simple regression with one predictor variable?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/heterogeneity#">What is heterogeneity of variance in SPSS Probit and Logit procedures?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/probitv6#">Why don't I see fiducial confidence intervals doing a probit analysis in version 16 of SPSS?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/meta#">Meta-analysis issues: 1) How do I measure publication bias? 2) How do I obtain a confidence interval for pooled estimates from sets of log odds, Cohen's d and Pearson correlations using a) meta-analysis and b) for Cohen's d as suggested for combining two studies to assess replication of a result?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/SumsOfSquaresTypes#">In ANOVA and Regression, what do the various different types of Sums of Squares mean, and does the choice matter?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/FVars#">What is the variance of the mean of my transformed data?</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/Interaction#">How do I work out the meaning of a significant interaction?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/contint#">How do I test for an interaction involving a continuous variable (moderation analysis)?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/hier#">What is the difference between a hierarchical and a stepwise regression? Also:a reference for an alternative, decision trees</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/stepints#">How do I perform a stepwise regression in SPSS involving interactions?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/intercept#">Interpreting the intercept term in a regression when covarying out predictors of within-subject difference scores</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/intuni#">What is the importance of including an intercept term in  the SPSS (between subjects ANOVA) univariate procedure?</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/constregSPSS#">How do I obtain covariance terms involving the intercept term in a linear regression using SPSS?</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/singcaserefs#">Are there any primer publications explaining rationale and application of single case studies?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/beta#">How do I compute linear trend coefficients for single cases?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/dummy#">How do I construct dummy variables for use in SPSS linear regression?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/singcase#">How do I compare a within subjects group difference to that of a single case?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/ancreg#">Can I do an analysis of covariance using a regression?</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/SobelTest#">How do I test whether one independent variable has an influence on a dependent variable other than via the mediation of a second independent variable? (Sobel Test)</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/causation#">Can I fit two-way links between variables in a path model?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/regline#">How do I put a regression line on a scatterplot in SPSS Version 12.0 and above?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/intcptr2#">Why does the R-squared change when I fix the intercept in my regression line from its least squares value?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/Collinearity#">What is Collinearity in multiple regression, and what do I do about it?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/condnoR#">How do I find the condition number of a matrix using R?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/facnum#">How do I convert a factor variable into a numeric in R?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/nom#">How do I perform a regression with a categorical outcome?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/iso#">How do I look for the best fitting model with an unknown changepoints on ordered data?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/dummyCor#">Regression diagnostics for categorical variables</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/wald#">What is the Wald statistic?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/x1se#">How do I compute the standard error of X1 in a regression also featuring X2?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/ab-a#">How do I interpret a regression involving variables A and B-A in predicting an outcome?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/covary#">How do I test to see if a mean adjusted for a covariate equal zero within a single group?</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/betase#">How do I compute the standard error of ''beta'' in a linear  regression in SPSS?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/ResidualsNonNormality#">Residuals and (Non-)Normality</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/AICreg#">How do I compute Akaike's and Bayesian information criteria (AIC, BIC) to compare regression models and how do I interpret them?</ulink>  </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/AdequateFit#">How well does a regression line fit?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/RegressionOutliers#">Checking for outliers in regression</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/infmles#">Why are the standard errors so large in logistic regression?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/texts#">Can you recommend any statistical textbooks?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/RatCaseVar#">Is there an optimal ratio of cases to predictor variables I should have before doing a regression?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/subsets#">How do I perform all possible subsets regression in SPSS?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/powprogs#">How do I do power calculations in SPSS?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/RegCor#">What is the relationship between significance tests of regression coefficients and of correlation coefficients?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/semiprinR#">How do I compute the semi-partial correlation coefficient in R?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/rsqdiff#">How do I compare two squared (semi-partial) correlation coefficients (R-squareds) from different samples?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/cohenrsq#">How do I compare two squared (semi-partial) correlation coefficients from the same sample?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/rsqadj#">How do I adjust R-squareds for the number of predictors in a model?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/multilevel#">What are random effect and multilevel models, when do I use them and are there effect sizes?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/mixedR#">Where can I find our about using random effects (including multilevel) models in R (including obtaining proportion of variance explained by a variable) &amp; in SPSS?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/hess#">What does an error message concerning the Hessian matrix suggest when running a mixed (random effects) model?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/ssq#">What does 's' denote when used to describe a General Linear Model (GLM)?</ulink> </para></listitem><listitem><para><ulink url="https://imaging.mrc-cbu.cam.ac.uk/statswiki/FAQ/regFAQ/statswiki/FAQ/gam#">What is a Generalized Additive (Mixed) Model (GA(M)M) and when do I use it?</ulink> </para></listitem></orderedlist></section></article>