In Exercises 6.15 to 6.18, what sample size is needed to give the desired margin of error in estimating a population proportion with the indicated level of confidence?6.15 A margin of error within 25% with 95% confidence. 6.16 A margin of error within +1% with 99% confidence. 6.17 A margin of error within +3% with 90% confidence. We estimate that the population proportion is about 0.3. 6.18 A margin of error within +2% with 95% confidence. An initial small sample has p = 0.78.