search for: alpha_k

...sociated with the levels in strata() within a clogit() model? I'm running R-1.9.0 on a Linux platform. I am using clogit() to run a Rasch model in Item Response Theory in psychometrics. Symbolically, the model is: logit(p_{j,k}) = \log({\Pr(p_{j,k}) \over \Pr(1-p_{j,k})}) = \theta_j - \alpha_k, That is, the log odds of answering an test item correctly is a function of the item difficulty (\theta_j) and the ability of individual students (\alpha_k). The following R syntax gives me the \theta coefficients associated with items i5 to i17, but summary() does not automatically summarize the...

Hello, Could someone give me a hint about what might be the difference between running urppTest with Z-alpha and Z-tau in type=c("Z-alpha", "Z-tau")? Is this the underlying equation: delta_y(t) = mu + tau*timetrend+(1-rho)*y(t-1) + alpha_1*delta_y(t-1) + ... + alpha_k*delta_y(t-k) + error term ? I looked at Banerjee et al. mentioned in the fSeries documentation, but that didn't help. Thanks a lot, Katrin

I feel bad even asking, but: Rgames> data(OrchardSprays) Rgames> model<-lm(decrease~.,data=OrchardSprays) Rgames> model Call: lm(formula = decrease ~ ., data = OrchardSprays) Coefficients: (Intercept) rowpos colpos treatmentB treatmentC 22.705 -2.784 -1.234 3.000 20.625 treatmentD treatmentE treatmentF treatmentG treatmentH

...Whitehead which is availabe at http://www.rdg.ac.uk/mps/mps_home/misc/publications.htm . There it is fit by using Proc NLMIXED. The result for beta is there: The problem is that alpha_{ik} represents the k_th intercept for the i_th study. A "normal" Proportional-Odds model has only alpha_k which represents the k-th intercept without any associaton to the study. I tried to fit it by using the functions of Pinheiro/ Bates nlme, nls, gnls; polr by Venables/Ripley ; lrm by Harrell ordgee by Yan; but I came to no conclusion. I would be very happy if anyone could help me....