Statistical modelling

We now change the order in which the effects are fitted so that GENOTYPE is added last. For the purposes of this output GenStat has also provided the predicted least squares means for each genotype (obtained by clicking the Predict button that appears after the model has been fitted ) together with their standard errors.

Note that the parameter estimates remain the same regardless of the order in which the terms are added to the model. However, compairing this output with the one given earlier in which the term GENOTYPE was fitted first, the mean square accounted for by GENOTYPE, after correcting for all the other terms in the model, is reduced from 190.142 to 25.286 kg2. This demonstrates the impact of the partial confounding of other factors, particularly year, on the variation that can be attributed uniquely to genotype. Genotype differences, nevertheless, remain significant (P < 0.01)

 
Response variate: WEANWT
    Fitted terms: Constant + YEAR + SEX + AGEWEAN + DL
                           + DQ + GENOTYPE
*** Estimates of parameters ***

estimate

s.e.

t(687)

Constant

0.25

1.07

0.23

YEAR 92

-1.565

0.293

-5.34

YEAR 93

-1.099

0.276

-3.99

YEAR 94

-2.820

0.359

-7.85

YEAR 95

-3.215

0.346

-9.30

YEAR 96

-2.342

0.391

-5.99

SEX M

0.476

0.170

2.81

AGEWEAN

0.07026

0.00886

7.93

DL

2.725

0.315

8.65

DQ

-0.269

0.034

-7.90

GENOTYPE RD

-0.389

0.220

-1.77

GENOTYPE RR

-1.040

0.271

-3.84

GENOTYPE DR

-0.511

0.304

-1.68

*** Accumulated analysis of variance ***

Change

d.f.

s.s.

m.s.

v.r.

+YEAR

5

1208.149

241.630

48.92

+SEX

1

55.983

55.983

11.34

+AGEWEAN

1

344.206

344.206

69.69

+DL

1

151.513

151.513

30.68

+DQ

1

275.795

275.795

55.84

+GENOTYPE

3

75.857

25.286

5.12

Residual

687

3392.947

4.939

  

Total

699

5504.450

7.875

  

GENOTYPE

Prediction

s.e.

DD

11.552

0.159

DR

11.041

0.240

RD

11.163

0.176

RR

10.512

0.193

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