One thousand Florida residents were asked if they would elect republican or democratic candidate for Governor in next election. 540 out of 1000 responded that they would vote for Democratic candidate. Which of the following statements correctly states how the confidence interval for population proportion of people which would vote for the democratic candidate should be computed?
A. There are not 15 successes and 15 failures. A confidence interval can't be done.
B. There are not 15 successes and 15 failures. A confidence interval can be calculated by adding 2 successes and 2 failures.
C. There are not 15 successes and 15 failures. A confidence interval can be calculated by adding 4 successes and 5 failures.
D. There are at least 15 successes and 15 failures. A large sample confidence interval for population proportion can be calculated (phat +/- z * sqrt(p*(1-p)/n) with no additional values added.