Repeated Measures Analysis Using Multilevel Modeling with SPSS David A. Kenny

* Presumed Background Multilevel Modeling Nested *

Data People Measured k Times Examples The k times are not replications as in diary study Each level of k represents a “condition” In principle, k measurements for every level 2 unit. Examples Baseline, Post-intervention, Follow-up Experimental Conditions

Crossed versus Nested In a standard multilevel design, observations are nested within the level 2 units. For a repeated measures design, observations are crossed with the level 2 units.

Problems with Repeated Measures ANOVA Assumes homogeneity of variance and equal correlation – compound symmetry – which is unlikely. Missing data on one or more of the measures: Need to throw out the entire case. Covariates, especially repeatedly measured covariates

Data Requirements Potentially k measurements for all some participants (may be missing data) Each level of the repeated measure can appear at the most once for each level 2 unit. Narrow format: Each record is one score for each person-measure combination Needs to have a participant (PID) and measure identifier (MEASURE) on the record Relevant factors and covariates on the record.

Example: Cook Anxiety Study The husband, the older child who is in college, and the younger child who is at home each states how anxious he or she feels toward the wife or mother of the family. 208 families and 624 family members Cook, W. L. (2000). Understanding attachment anxiety in family context. Journal Personal and Social Psychology, 78, 285-294.

Download Data Syntax Output

It aids the interpretation if the “Role” variable is not numeric.

No need to do anything here: Role a Factor, not a Covariate. Click this:

SPSS: Syntax MIXED Anxiety BY role /FIXED=role /PRINT=SOLUTION TESTCOV /REPEATED=role | SUBJECT(focalid) COVTYPE(UNR) /EMMEANS=TABLES(role) COMPARE ADJ(BONFERRONI).

Older child is less anxious with mother than either of the other two family members. Fathers and younger child do not significantly differ.

Could we treat family members as nested? Could treat members as nested, or … Choose “Compound Symmetry” as the repeated measures covariance structure. Subtract the two deviances. That difference tests the null hypothesis of compound symmetry. Test has 4 df 1 variance in CS versus 3 in unstructured 1 correlation in CS versus 3 in unstructured

Compound Symmetry Setup

Conclusion: Data do not support compound symmetry. Unstructured Run Compound Symmetry Run c2(4) = 1433.903 – 1402.497 = 31.406, p < .001 Conclusion: Data do not support compound symmetry.

* Thank You! William Cook *

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