# boscovich

 Nov 13 comment How can we derive Woolf's method?Also, this Woolf B. On estimating the relationship between blood group and disease. Human Genetics 1955; 19:251–253. and this Bagos P.G. On the covariance of two correlated log-odds ratios. Stat Med 2012; 31(14):1418–31 might be useful @yusuf Nov 13 comment What incentives can a faculty member offer to a potential lab manager?Very useful answer. As I'm considering to apply for one of those types of positions (as opposed to a postdoc) this was extremely helpful. +1. Nov 12 comment How can we derive Woolf's method?take a look at this technical report s3-us-west-1.amazonaws.com/hss-prod-storage.cloud.caltech.edu/… Sep 21 comment What is the average number of references in a PhD thesis?As always, PhD Comics has the answer to all your questions: phdcomics.com/comics/archive/phd091615s.gif Aug 20 comment Interpretation of $\mathbf{y}^T(\mathbf{I}-\mathbf{H})\mathbf{y}$ in OLSThank you very much. Great explanation. Aug 19 accepted Interpretation of $\mathbf{y}^T(\mathbf{I}-\mathbf{H})\mathbf{y}$ in OLS Aug 19 asked Interpretation of $\mathbf{y}^T(\mathbf{I}-\mathbf{H})\mathbf{y}$ in OLS Aug 5 comment Do you include papers that you contributed to but weren't cited as an author in on your CV? Jul 3 comment What causes differences in estimates of 95%CI of the mean across subgroups in Stata?What is causing such behavior is the choice of the degrees of freedom for the t distribution from which the quantiles necessary to the calculation of the Cis are derived. For example, in your first example 26.33333 - invttail(20, .025)*3.122499=19.819911, while in your second example 26.33333 - invttail(58, .025)*3.122499=20.082969 Jun 29 awarded Popular Question Jun 21 comment How to do Cox regression if we have a variable which violates an assumption?Do you mean that it violates the proportional hazards assumption? You can look into Cox models with time-dependent (or time-varying) coefficients. For example see here: Heinzl, H., & Kaider, A. (1997). Gaining more flexibility in Cox proportional hazards regression models with cubic spline functions. Computer methods and programs in biomedicine, 54(3), 201-208 Jun 17 comment Listing acknowledgments on CV May 27 comment What is the right way of computing baseline hazard rateBesides piecewise exponential models (Poisson) with splines to model the baseline hazard suggested by AdamO, an alternative is using Royston-Parmar models (flexible parametric survival models) Apr 16 comment PH assumption: categorical variable (1 category does not interact with time)Creating dummy variables beforehand is a possible way to go. In this example, the variable drug has 3 levels (2 dummy variables in the model), but I let only one of the 2 dummy variables (i.e. only one of the drugs, here) to interact with log(time): webuse cancer xi i.drug stcox i.drug, tvc(_Idrug_3) texp(log(_t)) - hope the syntax is clear Apr 14 comment Is $R^2$ useful or dangerous?@probabilityislogic Do you have a reference for the relation between $AIC$ and $R^2$? Mar 25 comment Discrepancy between metafor and weighted lm() standard errorsThe PDF manual for Stata's vwls command contains the answer to your question: stata.com/manuals13/rvwls.pdf See Section "Remarks and examples". Mar 14 comment Can p-value = <0.05 with CI that includes 0 using chi2 in Stata?Quickly: the standard errors used to calculate the test and the CI are different. Take a look at the PDF of the Stata User's Guide (help prtest). Mar 1 comment A Book for Multiple Regression and Multivariate analysisI really like Applied Regression Analysis by Draper and Smith. It covers also topic in which you might not be interested (ridge regression, nonlinear estimation, GLM...), but the parts on linear regression are outstanding, in my opinion. The chapters on the geometry of least squares are probably the best part of this book. Feb 22 comment Is the likelihood a true function?Why the bayesian tag? Feb 16 awarded Yearling