I have a dataset of 140 patients equally divided into 3 groups. The dependent variable is "moca" and can take integers between 0 and 30. It is a longitudinal study with a total of 4 time-points (variable time is "timepoint"). The group defining variable is "status". The independent variables are "age at recruitment", "education", "sex" and "timepoint". I am interested in differences in the behaviour of moca across time in the 3 groups. The variable defining different patients is "recordID"
This is the command that I used:
mixed moca i.status i.sex education ageatrecruitment timepoint || RecordID: timepoint
So my questions are:
1- does the command I am using make sense?
2- with this model the lines I get for each group are parallel (i.e. have the same slope and differ only for the intercept). I suspect they might have different slopes though, how could I test for that? My guess would be to run the same command separately for each group (using the option by), but then how could I compare them with a test (the suest command doesn't work with the mixed command).
3- my dependent variable is limited to integers between 0 and 30 and it might be that my regression line tends to an asymptote at 30, how could I test for that/implement this in my model?
I apologise if my question is unclear/too long.
This is the command that I used:
mixed moca i.status i.sex education ageatrecruitment timepoint || RecordID: timepoint
So my questions are:
1- does the command I am using make sense?
2- with this model the lines I get for each group are parallel (i.e. have the same slope and differ only for the intercept). I suspect they might have different slopes though, how could I test for that? My guess would be to run the same command separately for each group (using the option by), but then how could I compare them with a test (the suest command doesn't work with the mixed command).
3- my dependent variable is limited to integers between 0 and 30 and it might be that my regression line tends to an asymptote at 30, how could I test for that/implement this in my model?
I apologise if my question is unclear/too long.
Comment