A polling organization has been hired to conduct a survey to determine the proportion of people who are likely to support an upcoming ballot initiative. To help determine the size of the sample required for the main poll, a preliminary poll of 20 people is taken that yields the results below. (Yes indicates that the person will support the initiative, No indicates that they won't.)
Yes No No No No Yes No No No No No No No No No No No No No No
Based on the results of the peliminary poll, how large a sample is required for the main poll, assuming that the main poll should have a margin of error of 3.3% and a confidence level of 96.7%.