Question

Is the sample valid? what percent of students prefer caramel popcorn?

Answer 1

Is the sample valid?
 First you must see if the number of students in the table corresponds to the number of students surveyed that was 75.
 We have then:
 33 + 15 + 27 = 75
 We have then that:
 The sample is valid.

 what percent of students prefer caramel popcorn? 
 We can make the following rule of three to answer this question:
 75 ---> 100%
 27 ---> x
 Clearing x we have:
 x = (27/75) * (100)
 x = 36%
 36% percent of students prefer caramel popcorn