12.12.2012 Views

SAS/STAT 922 User's Guide: The MIXED Procedure (Book Excerpt)

SAS/STAT 922 User's Guide: The MIXED Procedure (Book Excerpt)

SAS/STAT 922 User's Guide: The MIXED Procedure (Book Excerpt)

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

4524 ✦ Chapter 56: <strong>The</strong> <strong>MIXED</strong> <strong>Procedure</strong><br />

<strong>The</strong> “Fit Statistics” table in Figure 56.13 contains basic information about the REML fit.<br />

Figure 56.13 Fit Statistics<br />

Fit Statistics<br />

-2 Res Log Likelihood 71.0<br />

AIC (smaller is better) 77.0<br />

AICC (smaller is better) 79.0<br />

BIC (smaller is better) 75.2<br />

<strong>The</strong> “Type 3 Tests of Fixed Effects” table in Figure 56.14 contains a significance test for the lone<br />

fixed effect, Gender. Note that the associated p-value is not nearly as significant as in the previous<br />

analysis. This illustrates the importance of correctly modeling correlation in your data.<br />

Figure 56.14 Type 3 Tests of Fixed Effects<br />

Type 3 Tests of Fixed Effects<br />

Num Den<br />

Effect DF DF F Value Pr > F<br />

Gender 1 3 7.95 0.0667<br />

An additional benefit of the random effects analysis is that it enables you to make inferences about<br />

gender that apply to an entire population of families, whereas the inferences about gender from the<br />

analysis where Family and Family*Gender are fixed effects apply only to the particular families in the<br />

data set.<br />

PROC <strong>MIXED</strong> thus offers you the ability to model correlation directly and to make inferences about<br />

fixed effects that apply to entire populations of random effects.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!