Hi Deepa,
I would suggest that you design a questionnaire yourself based on the various reasons why people leave and why the rest stay. The reason is that most of the time, when in an interview, you talk about the project (for fresh graduates), having designed a questionnaire leaves a good impression. There are a lot of formats available on the internet and in various books, but what's the point of following those when all you do is probably customize or simply administer the same to your population and draw conclusions.
Cheers,
Phalcon