Again, just answering that question in the affirmative is not going to result a decree of nullity. Also, that statistic includes the many, many “lack of form” petitions that are routinely run through Tribunals, although that’s not actually a canonical requirement.
The Tribunal is looking to see whether both parties understood the indissolubility of marriage (and I am going to tell you that you’ll meet very few people who go into marriage thinking that there are no grounds for divorce --for example, a lot of people will tell you that they would divorce an unfaithful spouse), the nature of marriage, and whether they had the psychological capacity to enter into it (Alcoholism and drug addiction are frequent factors in this)