New users choose sign in over app try-out in first use screen

We have an mobile application that allows new users to try the application as "ghost" users before signing up to become certified users. The application has a first use screen that tells users that it is OK to try the application out before signing up.

Still, our statistics show that users choose sign in, even though they don't have an account.

I personally think that the problem lies somewhere between the copy of the new user button and still prominent Sign in button. Or it could be users getting confused between sign in and sign up. These are the things we should look into.

Are there other things we should consider to investigate futher?