@RW1 – @Reebtoor has it almost exactly right. The actual chance is 2500/14,000 (18%), because they select the national winners in parallel with the corporate ones, so the around 1,000 kids receiving a corporate award aren’t actually competing for the national one. The school specific ones come later, after the national and corporate ones have been awarded.
Assuming you go to a big scholarship school, the national award does not prevent you from receiving the large supplemental award lots of folks on here are chasing, but it does supplant the small “official” award from the school, and is considered more prestigious (since only 18% of finalists receive one), and, ironically, valuable, even though it’s only a one-time $2500, because, as you already know, it can be used anywhere.
@Reebtoor is 1,000% correct about stats needed to win varying from state to state, because the national awards are distributed proportionally, just like semifinalists are, so it’s somewhat easier to win in a lower SI cutoff state than in a higher one.