Journal ArticleDOI
Statistical analysis of repeated measures data using SAS procedures.
TLDR
This procedure implements random effects in the statistical model and permits modeling the covariance structure of the data, and can compute efficient estimates of fixed effects and valid standard errors of the estimates in the SAS System.Abstract:
Mixed linear models were developed by animal breeders to evaluate genetic potential of bulls. Application of mixed models has recently spread to all areas of research, spurred by availability of advanced computer software. Previously, mixed model analyses were implemented by adapting fixed-effect methods to models with random effects. This imposed limitations on applicability because the covariance structure was not modeled. This is the case with PROC GLM in the SAS® System. Recent versions of the SAS System include PROC MIXED. This procedure implements random effects in the statistical model and permits modeling the covariance structure of the data. Thereby, PROC MIXED can compute efficient estimates of fixed effects and valid standard errors of the estimates. Modeling the covariance structure is especially important for analysis of repeated measures data because measurements taken close in time are potentially more highly correlated than those taken far apart in time.read more
Citations
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The aligned rank transform for nonparametric factorial analyses using only anova procedures
TL;DR: This work presents the Aligned Rank Transform (ART) for nonparametric factorial data analysis in HCI, and re-examination of some published HCI results exhibits advantages of the ART.
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Neutrophil function and energy status in Holstein cows with uterine health disorders.
TL;DR: In this paper, the authors investigated the associations between peripheral blood neutrophil (PMN) function, energy status, and uterine health in periparturient dairy cows.
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Influence of Body Condition Score on Relationships Between Metabolic Status and Oxidative Stress in Periparturient Dairy Cows
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Relationship between follicle size at insemination and pregnancy success.
George A. Perry,Michael F. Smith,Matthew C. Lucy,Jonathan A. Green,Tina E. Parks,Michael D. MacNeil,Andrew J. Roberts,Thomas W. Geary +7 more
TL;DR: Administration of GnRH to induce ovulation likely initiates a preovulatory gonadotropin surge before some dominant follicles attain physiological maturity, which has a negative impact on pregnancy rates and late embryonic/fetal survival in cattle.
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The use of MIXED models in the analysis of animal experiments with repeated measures data
TL;DR: The objective of this paper is to provide a background understanding of mixed model methodology in a repeated measures analysis and to use balanced steer data from a growth study to illustrate the use of PROC MIXED in the SAS system using five covariance structures.
References
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Journal ArticleDOI
Maximum Likelihood Approaches to Variance Component Estimation and to Related Problems
TL;DR: In this paper, the authors proposed a restricted maximum likelihood (reml) approach which takes into account the loss in degrees of freedom resulting from estimating fixed effects, and developed a satisfactory asymptotic theory for estimators of variance components.
Journal ArticleDOI
Conditions under Which Mean Square Ratios in Repeated Measurements Designs Have Exact F-Distributions
Huynh Huynh,Leonard S. Feldt +1 more
TL;DR: In this paper, the character of the covariance matrix is investigated and it is shown that the matrix may exhibit a more general character than is typically implied to be essential, and the necessary and sufficient condition is the equality of variances of differences for all pairs of treatment measures assumed to be correlated.