Linear mixed models are popular models for use with clustered and longitudinal data due to their ability to model variation at different levels of clustering. A Monte Carlo study was used to explore the impact of assumption violations on the bias of parameter estimates and the empirical type I error rates. Simulated conditions included in this study are: simulated serial correlation structure, ...

In process robustness studies, it is desirable to minimize the influence of noise factors on the system and simultaneously determine the levels of controllable factors optimizing the overall response or outcome. In the cases when a random effects model is applicable and a fixed effects model is assumed instead, an increase in the variance of the coefficient vector should be expected. In this pa...

Records on 65,536 Landrace pigs collected between 1985 and 1999 in herds on the National Swine Registry STAGES program were used to estimate additive genetic (animal), common environmental (litter), and residual variances and covariances for days to 250 lb, backfat, loin eye area, and lean growth rate. Analysis was by the REMLf90 program of I. Misztal using a multiple-trait animal model with fi...

Random effect analysis has been introduced into fMRI research in order to generalize findings from the study group to the whole population. Generalizing findings is obviously harder than detecting activation within the study group since in order to be significant, an activation has to be larger than the inter-subject variability. Indeed, detected regions are smaller when using random effect ana...

Tensor product smooths provide the natural way of representing smooth interaction terms in regression models because they are invariant to the units in which the covariates are measured, hence avoiding the need for arbitrary decisions about relative scaling of variables. They would also be the natural way to represent smooth interactions in mixed regression models, but for the fact that the ten...

Two previous meta-analyses concluded that average validity coefficients for the Rorschach and the MMPI have similar magnitudes (L. Atkinson, 1986; K. C. H. Parker, R. K. Hanson, & J. Hunsley, 1988), but methodological problems in both meta-analyses may have impeded acceptance of these results (H. N. Garb, C. M. Florio, & W. M. Grove, 1998). We conducted a new meta-analysis comparing criterionre...

Mutual Fund industry plays a pivotal role in optimal allocation and channelization of available idle resources in the economy. This role becomes much stronger in the developing economies like Pakistan where the prospective investors do not have much investment knowledge, information, and facilities to invest in the capital markets neither they have risk aptitude for direct investments in risky ...

Meta-analysis is now commonly used in medical research. However there are statistical issues relating to the subject that require investigation and some are considered here, from both a methodological and a practical perspective. Each of the fixed effect and the random effects models for meta-analysis are based on certain assumptions and the validity of these is investigated. A formal test of t...

Based on the Q-function, the conditional expectation of the logarithm of the jointlikelihood between responses and random effects, we propose a case-deletion approach to identify influential subjects and influential observations in linear mixed models. The models considered here are very broad in the sense that any covariance structures can be specified in the covariance matrices of the random ...

This paper e.vatnines whether a severe flood causes homeowners to update their assessment of ßood risk as seen in a change in the price of fhodphtin property. I use data on all single-family. residential property sales in St, Louis County. Missouri, hetweeti 1979 and 2006 in a repeat-sales model and a property fixed-effects model. After the ¡993 ßood on the Mi.ssouri and Mississippi rivers, pro...