I was accepted to some top stat PhD programs this year. But...

[kasuganosora]

I was accepted to some top stat PhD programs this year. All are ranked in the top 15.  I am interested in some topics. However, honestly, I am not sure what I want to research. There is a possibility that I will change my mind in the future.

Is it unusual to quit PhD program in the middle and get into another PhD program again?
(I know such cases occur when supervisors move to other schools. But other than that...)

[GoPackGo89]

Wouldn't it make sense to just change problems or find a new advisor within the department? Interested in an answer as well

[StatsG0d]

I would say unusual is a bit of an understatement. More like "extremely rare". These universities spend a lot of money funding you, so if you quit, it might signal to the new university that you aren't really sure what you're getting yourself into. Just something to think about.