== Questions about linear regression == 1. [[FAQ/E|What does a number containing an 'E' signify?]] 1. [[FAQ/pearson|What is the relationship between the Pearson correlation and a simple regression estimate?]] 1. [[FAQ/suppress|What is the relationship between predictor variable correlations and the presence of a suppressor variable?]] 1. [[FAQ/studentres|How do I check for outliers in a simple regression with one predictor variable?]] 1. [[FAQ/heterogeneity| What is heterogeneity of variance in SPSS Probit and Logit procedures?]] 1. [[FAQ/probitv6| Why don't I see fiducial confidence intervals doing a probit analysis in version 16 of SPSS?]] 1. [[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?]] 1. [[FAQ/SumsOfSquaresTypes|In ANOVA and Regression, what do the various different types of Sums of Squares mean, and does the choice matter?]] 1. [[FAQ/FVars| What is the variance of the mean of my transformed data?]] 1. [[FAQ/Interaction|How do I work out the meaning of a significant interaction?]] 1. [[FAQ/contint|How do I test for an interaction involving a continuous variable (moderation analysis)?]] 1. [[FAQ/hier|What is the difference between a hierarchical and a stepwise regression? Also:a reference for an alternative, decision trees]] 1. [[FAQ/stepints|How do I perform a stepwise regression in SPSS involving interactions?]] 1. [[FAQ/intercept| Interpreting the intercept term in a regression when covarying out predictors of within-subject difference scores]] 1. [[FAQ/intuni| What is the importance of including an intercept term in the SPSS (between subjects ANOVA) univariate procedure?]] 1. [[FAQ/constregSPSS| How do I obtain covariance terms involving the intercept term in a linear regression using SPSS?]] 1. [[FAQ/singcaserefs| Are there any primer publications explaining rationale and application of single case studies?]] 1. [[FAQ/beta| How do I compute linear trend coefficients for single cases?]] 1. [[FAQ/dummy| How do I construct dummy variables for use in SPSS linear regression?]] 1. [[FAQ/singcase| How do I compare a within subjects group difference to that of a single case?]] 1. [[FAQ/ancreg|Can I do an analysis of covariance using a regression?]] 1. [[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)]] 1. [[FAQ/causation|Can I fit two-way links between variables in a path model?]] 1. [[FAQ/regline|How do I put a regression line on a scatterplot in SPSS Version 12.0 and above?]] 1. [[FAQ/intcptr2|Why does the R-squared change when I fix the intercept in my regression line from its least squares value?]] 1. [[FAQ/Collinearity|What is Collinearity in multiple regression, and what do I do about it?]] 1. [[FAQ/condnoR| How do I find the condition number of a matrix using R?]] 1. [[FAQ/facnum| How do I convert a factor variable into a numeric in R?]] 1. [[FAQ/nom| How do I perform a regression with a categorical outcome?]] 1. [[FAQ/iso| How do I look for the best fitting model with an unknown changepoints on ordered data?]] 1. [[FAQ/dummyCor|Regression diagnostics for categorical variables]] 1. [[FAQ/wald|What is the Wald statistic?]] 1. [[FAQ/x1se|How do I compute the standard error of X1 in a regression also featuring X2?]] 1. [[FAQ/ab-a|How do I interpret a regression involving variables A and B-A in predicting an outcome?]] 1. [[FAQ/covary|How do I test to see if a mean adjusted for a covariate equal zero within a single group?]] 1. [[FAQ/betase|How do I compute the standard error of ''beta'' in a linear regression in SPSS?]] 1. [[FAQ/ResidualsNonNormality|Residuals and (Non-)Normality]] 1. [[FAQ/AICreg|How do I compute Akaike's and Bayesian information criteria (AIC, BIC) to compare regression models and how do I interpret them?]] 1. [[FAQ/AdequateFit|How well does a regression line fit?]] 1. [[FAQ/RegressionOutliers|Checking for outliers in regression]] 1. [[FAQ/infmles|Why are the standard errors so large in logistic regression?]] 1. [[FAQ/texts| Can you recommend any statistical textbooks?]] 1. [[FAQ/RatCaseVar|Is there an optimal ratio of cases to predictor variables I should have before doing a regression?]] 1. [[FAQ/subsets| How do I perform all possible subsets regression in SPSS?]] 1. [[FAQ/powprogs|How do I do power calculations in SPSS?]] 1. [[FAQ/RegCor|What is the relationship between significance tests of regression coefficients and of correlation coefficients?]] 1. [[FAQ/semiprinR|How do I compute the semi-partial correlation coefficient in R?]] 1. [[FAQ/rsqdiff|How do I compare two squared (semi-partial) correlation coefficients (R-squareds) from different samples?]] 1. [[FAQ/cohenrsq|How do I compare two squared (semi-partial) correlation coefficients from the same sample?]] 1. [[FAQ/rsqadj|How do I adjust R-squareds for the number of predictors in a model?]] 1. [[FAQ/multilevel| What are random effect and multilevel models, when do I use them and are there effect sizes?]] 1. [[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) & in SPSS?]] 1. [[FAQ/hess| What does an error message concerning the Hessian matrix suggest when running a mixed (random effects) model?]] 1. [[FAQ/ssq| What does 's' denote when used to describe a General Linear Model (GLM)?]] 1. [[FAQ/gam| What is a Generalized Additive (Mixed) Model (GA(M)M) and when do I use it?]]