2. Use the linear mixed model (also called growth curve model) for children's bone length data. Briefly, bone length (ou

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2 Use The Linear Mixed Model Also Called Growth Curve Model For Children S Bone Length Data Briefly Bone Length Ou 1 (34.45 KiB) Viewed 33 times

2. Use the linear mixed model (also called growth curve model) for children's bone length data. Briefly, bone length (outcome) was measured at ages 8, 8.5, 9, and 9.5. We fit a linear mixed model to predict bone length using a random intercept and slope (for age), and fixed age, i.e., proc mixed data=bone method=reml covtest; = class subject; model y=age/s; random int age/type=un subject=subject; run;

Dimensions Covariance Parameters 4 Columns in X 2 Columns in Z Per Subject 2 Subjects 38 Max Obs Per Subject 4 Number of Observations Number of Observations Read 152 Number of Observations Used 152 Number of Observations Not Used 0 Covariance Parameter Estimates Cov Parm Subject Estimate Standard Error Z Value Pr Z UN(1,1) subject 116.77 30.8713 3.78 <.0001 UN(2,1) subject -12.4063 3.3620 -3.69 0.0002 UN(2,2) subject 1.4157 0.3776 3.75 <.0001 Residual 0.2531 0.04106 6.16 <.0001 Null Model Likelihood Ratio Test DF Chi-Square Pr > Chisa 3 272.92 <.0001 Solution for Fixed Effects Effect Estimate Standard Error DF t Value Pr > |t| Intercept 30.4895 1.8662 37 16.34 <.0001 age 2.1605 0.2064 37 10.47 <.0001 Type 3 Tests of Fixed Effects

Effect Num DF Den DF F Value Pr>F age 1 37 109.62 <.0001 a. Write out the Xi matrix for this model. b. Are the random intercept and random age term appropriate for this model? c. If we add sex to the model, the covariate does not significantly predict bone growth. Should we leave sex in the model? Why or why not?