To answer this question I used ratio table and x k y chart. The bubbleshare below shows my work. I did it step by step so you guys can understand it.
So from the bubbleshare above, you can see that 40% of 37 students is 14.8 .To double check my answer I used cross multiplying and equivalent fractions. I also did it step by step so it is easier to understand and follow.
So by double checking I am now sure my answer is correct. So 40% of 37 students is really 14.8.
If then the answer is 14.8, that will prove that David's is INCORRECT! His claim is that exactly 40% of his 37 interviewed students liked vanilla best. Since we are talking about students we can't have decimals. So that proves that he is incorrect.
If David argued that my reasoning is wrong and he suggested that I round it. Then I'll prove to to him that even if you round it he is still wrong. Look below!
Round 14.8 = 15
40/ 100 = 0.4
0.4 x 100 (percent is out of 100) = 40%
15/37 = 0.405405405
0.405405405 x 100 (percent is out of 100) = 40.5405405%
Then if you round 40.5405405% to the nearest ones, you'll get 41%
Therefore David is INCORRECT!
IF I MADE A MISTAKE, I WOULD APPRECIATE IT IF YOU TELL ME.