英语中否定转移时,反义疑问句看从句,如果不否定看什么?与主句时态有关吗

看例子你就明白了,说多了反倒不明白.
I don't think he is a student,is he?
I think he is a student,isn't he?
He doesn't think you are a student,does he?
He thinks you are a student,doesn't he?
He didn't think you were a student,did he?
He thought you were a student,did he?