A survey is run in a country of approximately 5 million people. The survey is held in order to estimate what proportion of people in the country have a certain characteristic. Roughly 1,000 people are surveyed, and a sample proportion is calculated. The surveyor then wishes to construct a confidence interval for the population proportion. Select the pieces of information that the surveyor requires in order to construct the confidence interval:

a. the exact size of the sample that is surveyed
b. the proportion of people in the sample with the characteristic
c. the characteristic of interest the exact size of the population
d. the level of confidence desired