> the only thing i can not understand is why psu is school_id,but not distric_id or sub-distric_id?
I'll leave that up to the statitians, but in another survey software SUDAAN you can
specify more than 2 levels to correct for. I believe what you can do in Stata to
achieve the same thing is to combine your district id variable with your sub-district_id
variable so that one variable specifies a sub-district for example if your data looked like this:
district sub_district
100 1
100 2
101 1
101 2
101 3
You could :
gen dis_sub = (district*10)+sub_district
which would look like this:
district sub_district dis_sub
100 1 1001
100 2 1002
101 1 1011
101 2 1012
101 3 1013
Hope this helps,
Dan Blanchette
Carolina Population Center UNC-CH