Using the given margin of error, confidence level, and likely range for the observed value of the sample proportion, obtain a sample size that will ensure a margin of error of at most the one specified (provided, of course, that the observed value of the sample proportion is further from 0.5 than the educated guess). margin of error 0.015; confidence level 95%; likely range = 0.15 to 0.35 The required sample size is n = (Round up to the nearest whole number.)