Re: Diagnosing and addressing collinearity in Survival Analysis
On 06 Jun 2001 06:46:55 GMT, [EMAIL PROTECTED] (ELANMEL) wrote: Any assistance would be appreciated: I am attempting to run some survival analyses using Stata STCOX, and am getting messages that certain variables are collinear and have been dropped. Unfortunately, these variables are the ones I am testing in my analysis! If there are 3 groups (classes), then you can have only two dummy variables to refer to their degrees of freedom. You can code those in the most convenient and informative way. If your problem arises otherwise, then you have a fundamental problem in the logic of what is being tested. Google shows some examples of problems when I search for statistical confounding (use the quotes for the search). And confounded designs seems to obtain discussions. I would appreciate any information or recommendations on how best to diagnose and explore solutions to this problem. -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: please help
On 10 Jun 2001 07:27:55 -0700, [EMAIL PROTECTED] (Kelly) wrote: I have the gage repeatability reproducibility(gage RR) analysis done on two instruments, what hyphoses test can I use to test that the repeatability variance(expected sigma values of repeatability) of the two instruments are significantly different form each other or to say one has a lower variance than the other. Any insight will be greatly appreciated. Thanks in advance for your help. I am not completely sure I understand, but I will make a guess. There is hardly any power for comparing two ANOVAs that are done on different samples, until you make strong assumptions about samples being equivalent, in various regards. If ANOVAs are on the same sample, then a CHOW test can be used on the improved prediction if one hypothesis consists of an extra d.f. of prediction. If ANOVAs are on separate samples, I wonder if you could compare the residual variances, by the simple variance ratio F-test -- well, you could do it, but I don't know what arguments should be raised against it, for your particular case. There are criteria resembling the CHOW test that are used less formally, for incommensurate ANOVAs (not the same predictors) - AKAIKE and others. If your measures are done on the same (exact) items, you might have a paired test. Instrument A gets closer values on how many of the measurements that are done. Finally, if you can do a bunch of separate experiments, you can test whether A or B does better in more than half of them. -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Kendall tau and Kendall's partial tau
To compute Kendall's tau-b rank correlation, you can use PROC CORR in SAS: proc corr kendall data=data set name; var variable names; run; For partial correlations, add the PARTIAL statement, e.g. PARTIAL z; * Z is the name of the variable you want to partial out; HTH, Vadim Pliner [EMAIL PROTECTED] (Monica De Stefani) wrote in message news:[EMAIL PROTECTED]... Hi everybody, my name is Monica De Stefani and I would known how Kendall rank correlation coefficient and Kendall's partial tau can be applied to a time series using x(t) and x(t-j) (x=time series, j=lag) instead two random variable x and y. I would known if exist any software for kendall and kendall's partial tau methods. Thanks. Monica De Stefani. = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Online data for psychology/education?
Do you know where I can find experimental data sets regarding psychology or/and education posted on the Web? I tried several search engines but did not find much. If anyone has posted data on the Web, your info will be helpful. Thanks. Chong-ho (Alex) Yu, Ph.D., MCSE, CNE Academic Research Professional/Manager Educational Data Communication, Assessment, Research and Evaluation Farmer 418 Arizona State University Tempe AZ 85287-0611 Email: [EMAIL PROTECTED] URL:http://seamonkey.ed.asu.edu/~alex/ = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
