It varies a lot from person to person. There is no way to accurately tell. If you the applicant does a horrible job at the interview, the rejection within 2 weeks is inevitable.
This is not an interview in the traditional sense. In fact, there is generally no way to do a horrible job at this interview. What the applicant is doing at this interview, is to recount all the events that happened, and to articulate basis of credible fear in the future, and finally, to answer questions from the asylum officer. So, normally, people don't do a horrible job at the interview.
Exceptions:
1. Applicant can't re-call the events of persecution in the past, doesn't know obvious dates
2. Applicant is arguing with the asylum officer
3. Applicant is throwing tantrums, swearing at the asylum officer
4. Applicant is acting as if he/she is entitled to asylum
5. Applicant is making up stuff, doesn't answer questions asked, etc.
If your interview falls in any of the above category (and others I haven't mentioned), then yeah, "you are doing a horrible job at your interview" as my good friend
@msv5450 has said.