Hello statisticians, When I run the proc mixed model on longitudinal complex survey data, I found only one of the interaction year_mixed*age (when age=64) is not calculated each time. proc mixed data=sample;
class PN age (ref='50') ;
model Score=year_mixed age year_mixed*age /solution cl;
random intercept year_mixed/ subject=PN type=un;
weight wt;
run;quit; In this study, PN is the participant's ID, age is the year of age their scores were measured, and year_mixed is the date the score was measured (a continuous variable). I currently consider age categorical, and the level of PN is 22648, the level of Age is 15, total observation used is 78028 after weight. I also tried randomly selecting some small samples n=3000 to run the code the interaction year_mixed*age(64) is still missing and not calculated as I show in the result below. Type 3 Tests of Fixed Effects Effect Num DF Den DF F Value Pr > F year_mixed 1 1.90E+04 0.91 0.339 age 14 3.70E+04 3.48 <.0001 year_mixed*age 13 3.70E+04 0.81 0.65 I am wondering why when age=64 the year_mixed*age is not calculated. My other categorical variates work fine, they call can be calculated (Race, Education, Et al.). I really appreciate your help! Thanks, Jess
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