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Brian S. Everitt A Handbook of Statistical Analyses using SPSS

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Iteration<br />

0<br />

1<br />

2<br />

3<br />

4<br />

5<br />

6<br />

7<br />

8<br />

Update Type<br />

Fixed<br />

Effects<br />

Random<br />

Effects<br />

Residual<br />

Total<br />

Intercept<br />

TREAT<br />

C_MONTH<br />

C_PRE<br />

Intercept<br />

C_MONTH<br />

Number<br />

<strong>of</strong> Levels<br />

Model Dimension a<br />

Covariance<br />

Structure<br />

Number <strong>of</strong><br />

Parameters<br />

Subject<br />

Variables<br />

1 1<br />

1 1<br />

1 1<br />

1 1<br />

1 Identity 1 SUBJECT<br />

1 Identity 1 SUBJECT<br />

1<br />

6 7<br />

a. Dependent Variable: Post-treatment depression score.<br />

Number <strong>of</strong><br />

Step-halvings<br />

Iteration History b<br />

Covariance Parameters<br />

Fixed Effect Parameters<br />

Intercept C_MONTH<br />

-2 Restricted<br />

[subject = [subject =<br />

Log<br />

SUBJECT] SUBJECT]<br />

Likelihood Residual ID diagonal ID diagonal Intercept TREAT C_MONTH C_PRE<br />

Initial 0 2021.046 26.14744 26.1474442 26.1474442 16.67599 -5.27073 1.1903886 .5125490<br />

Scoring 1 1964.729 25.43479 41.2184411 2.8328789 16.63831 -4.50924 1.0287282 .5522275<br />

Scoring 1 1926.724 24.90006 49.2784441 6.1882973 16.65211 -3.94426 -.8923691 .5796988<br />

Scoring 1 1900.683 24.52781 52.9800480 3.0078202 16.67899 -3.59681 -.8017594 .5966415<br />

Scoring 0 1875.382 24.04293 55.3249894 3.865E-02 16.71171 -3.20019 -.7000578 .6172862<br />

Scoring 0 1874.882 23.96467 52.7822184 .2091313 16.70738 -3.23882 -.7087159 .6153676<br />

Newton 0 1874.880 23.96393 53.0260027 .2012500 16.70778 -3.23618 -.7081400 .6154884<br />

Newton 0 1874.880 23.96392 53.0277710 .2013409 16.70778 -3.23619 -.7081412 .6154881<br />

Newton 4 1874.880 a 23.96392 53.0277710 .2013409 16.70778 -3.23619 -.7081412 .6154881<br />

a. All convergence criteria are satisfied.<br />

b. Dependent Variable: Post-treatment depression score .<br />

Parameter<br />

Residual<br />

Intercept [subject = ID diagonal SC]<br />

C_MONTH [subject ID diagonal SC]<br />

a. Dependent Variable: Post-treatment depression score .<br />

Estimates <strong>of</strong> Covariance Parameters a<br />

95% Confidence Interval<br />

Estimate Std. Error Wald Z Sig. Lower Bound Upper Bound<br />

23.96392 .9905226 8.013 .000 18.7643740 30.6042397<br />

53.02777 .2225126 5.750 .000 37.7106173 74.5663874<br />

.2013409 .2975969 .677 .499 .111200E-02 3.6481403<br />

Display 8.15 Part <strong>of</strong> random intercept and slope model output for BtB data.<br />

The Wald test (Wald z = 0.68, p = 0.5) demonstrates that the variance<br />

<strong>of</strong> the random slope effects is not significantly different from zero and<br />

here the simpler random intercept model provides an adequate description<br />

<strong>of</strong> the data. This might be because there is little departure <strong>of</strong> the observed<br />

correlation matrices in each treatment group from the compound symmetry<br />

structure allowed by the random intercept model, but it could also be a<br />

result <strong>of</strong> the random slope model we used being too restrictive since it<br />

did not allow for a possible correlation between the random intercept<br />

and random slope terms. <strong>SPSS</strong> version 11.0.1 (the one used in this text)<br />

does not allow for such a correlation, although version 11.5 and higher<br />

will allow this correlation to be a parameter in the model.<br />

The final model chosen to describe the average pr<strong>of</strong>iles <strong>of</strong> BDI scores<br />

in the two groups over the four post-treatment visits is one that includes<br />

© 2004 by Chapman & Hall/CRC Press LLC

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