Arandom sample of 100 undergraduate students at a university found that 78 of them had used the university library’s website to find resources for a class. what is the margin of error for the true proportion of all undergraduates who had used the library’s website to find resources for a class?

It depends upon the confidence level (99%, 95%, etc) of the sample. In this case, the population size is 100, and the sample size is 78. If it's in a 99% confidence level, margin of error is 7 (So between 71 - 85 undergrads). If it's in a 95% confidence level, the margin of error is 6 (So between 72 - 84 undergrads). 

Set square i think so