PROC MIXED

The statistical software package SAS (SAS Institute Inc., Cary, North Carolina, U.S.A.) has a module [PROC MIXED (10)], which analyzes mixed effects models and provides estimates for both the fixed (shifts on the mean) and random effects (variance components estimates). 

Accuracy is estimated from the fixed effects components of the model. If the overall mean is the only fixed effect, then accuracy is reported as the estimate of the overall mean accuracy with a 95% confidence interval. As the standard error will be calculated from a variance components estimate including intermediate precision components and repeatability, the degrees of freedom can be calculated using Satterthwaite s approximation (6). The software program SAS has a procedure for mixed model analysis (PROC MIXED) PROC MIXED has an option to use Satterthwaite s degrees of freedom in calculating the confidence interval for the mean accuracy. An example program and output is shown later for the example protocol. 

SAS PROC MIXED is used to analyze the data. For accuracy, the SAS code used is ... 

This program will give variance estimates for each of the precision components along with two-sided 95% confidence intervals for the population variance component for each expected mass. SAS PROC MIXED will provide ANOVA estimates, maximum likelihood estimates, and REML estimates the default estimation, used here, is REML. 

Wolfinger, R.D. Heterogeneous variance-covariance structures for repeated measures. Journal of Agricultural, Biological, and Environmental Statistics 1996 1 205-230. Wolfinger, R.D. An example of using mixed models and PROC MIXED for longitudinal data. Journal of Biophar-maceutical Statistics 1997 7 481-500. 

Recent advances in statistical software have brought the use of hierarchical linear models and stochastic regression models into easy reach. PROC MIXED in the SAS software package (SAS Institute, Inc.) and BMDP 5V in the Biomedi-... 

Statistical Analysis. Analyses were performed for intent-to-treat and per protocol samples with SAS, version 8.0 software (Cary, NC). ANOVA models were generated utilizing the PROC MIXED procedure. Repeated-measures ANOVA was employed to assess effects of treatment, time (week), and treatment X time interactions for the percentage of change from baseline in body weight, fat mass, and lAF area. 

Streiff, F. A., P. Mathys, and T. U. Fischer (1997). New fundamentals for liquid-liquid dispersion in static mixers, Proc. Mixing IX, Paris, pp. 307-314. 

Data were fitted by linear regression, employing the Random Coefficient Model of PROC MIXED [3] in SAS (SAS Inst. Inc.). Differences between regression lines were examined for statistical significance at the 95% level of confidence. 

The trial consisted of 6 consecutive periods (3 d of adaptation + 1 d of expired CO2 and plasma collection). On collection day, tracer phenylalanine was given orally in 8 A-hourly meals and expired [ l]-labelled CO2 was quantified. Data was analyzed using the Proc Mixed procedure in SAS (2001) where nesting THR intake within type of THR addition (e.g. free THR or THR in com or barley) gave the change (slope) in PHE oxidation per g of THR for each type of THR addition. The MAof THR in com and barley was calculated by dividing the slope for THR from the respective feedstuff by the slope for free THR. 

Data were analyzed as a mixed model with repeated measures using the PROC MIXED of SAS (SAS Inst Inc., Cary, NC). The statistical model included Ml (SAB, LAB and protozoa), F C, FOR, period, MlxF C, MtxpOR, FiCxpOR, MlxpiCxpOR as fixed effects, and sheep as a random effect Effects were declared significant at P<0.05. 

Statistical analysis was conducted using PROC MIXED of SAS (2006). 

Differences in BW and total feed intake in each experiment were analyzed using the PROC GLM procedure in SAS (2004) with main effects of phenotype, feeding program, trial, and their interactions included in the model. Intake of the HP and LP diets in pigs in the Choice treatment, were also analyzed as repeated measures using the PROC Mixed procedure in SAS (2004). The model included fixed effects of phenotype, day, and day x phenotype and the random effects of pig within phenotype and trial. 

---