Hi,   I have a few questions about longitudinal analysis with different start time and time intervals. In my study, I have six time points where BMI is measured in two groups of participants: Time1: Beginning of school year 1. Time2: End of school year 1. Time3: Beginning of school year 2. Time4: End of school year 2. Time5: Beginning of school year 3. Time6: End of school year 3.   There is summer break between each end of school year and beginning of next school year (eg. Summer break between time 2 and time 3). Currently, I used mixed model and only included participants who completed all six timepoint:   proc mixed data=data method=ML; class id time(ref="1")  group(ref="1")  ; model bmi =  time group time*group/ s outp=predicted residual; repeated time/type=un subject=id  ; run;   As the study continues with more time add down the road, I want to expand my sample by including 1) participants with different start point, such as including people who only start at time 3; and 2) people who miss one school year in between, such as people who participate in school year 1 and 3, but miss school year 2.   Do you have any tips on how to modify the model?   Thanks! SY ... View more

Hi, I have a question about the NOT EQUAL operator and hope you can help. I want to compare the variable i created ("hours3") against the original data "hours1" and "hours2". Below is my code. data check1; set example; where hours1^=hours3 or hours2^=hours3; keep id hours1 hours2 hours3 ; run;   However, SAS ouput lots of observations that the three variables values are actually EQUAL.   id hours1 hours2 hours3 1 254.4 254.4 254.4 2 243.2 243.2 243.2 3 290.9 290.9 290.9 4 291.9 291.9 291.9 5 202.2 202.2 202.2 I also made sure the format of three variables are the same but SAS still output values that are actually EQUAL. May I know what is the problem? Thanks!     ... View more