Answer:
1,600 of the 2,000 significantly improved
Explanation:
I will just show you the mathematics behind the question, but will leave the rest up to you:
We are trying to find what is 80% of the 2,000 people to see how many the ointment helped and not helped:
2000 x 0.8 = 1600, therefore the ointment helped 1,600 of the 2,000.
2000 - 1600 = 400, therefore the ointment did not help 400 of the 2,000.
I would guess that it is a valid conclusion, as 80% of 2,000 test helped, which would mean it most likely will help with most people. But, if it was something like 80% of 10 people, that would almost be like random chance, but because 2,000 is a high number, it most likely does help.
Hope I helped :)