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A researcher wishes to estimate, with 90% confidence, the population proportion of adults who think Congress is doing a good or excellent job. Her estimate must be accurate within 3% of the true proportion. (a) No preliminary estimate is available. Find the minimum sample size needed. (b) Find the minimum sample size needed, using a prior study that found that 18% of the respondents said they think Congress is doing a good or excellent job. (c) Compare the results from parts (a) and (b). (a) What is the minimum sample size needed assuming that no prior information is available? n= (Round up to the nearest whole number as needed.) (b) What is the minimum sample size needed using a prior study that found that 34% of the respondents said they think Congress is doing a good or excellent job? n= Round up to the nearest whole number as needed.) (c) How do the results from (a) and (b) compare? A. Having an estimate of the population proportion raises the minimum sample size needed. B. Having an estimate of the population proportion reduces the minimum sample size needed. C. Having an estimate of the population proportion has no effect on the minimum sample size needed.Translate the statement into a confidence interval. Approximate the level of confidence. In a survey of 3303 adults in a country, 45% believe the economy is getting better. Three weeks prior to this survey, 55% believed that the economy was getting better. The survey's margin of error is + 1%. Use the results from the newer survey. The confidence interval for the proportion is ( ). (Round to three decimal places as needed.) Use the results from the newer survey. The interval is a % confidence interval. (Round to one decimal place as needed.) Use the results from three weeks prior to the newer survey. The confidence interval for the proportion is (Round to three decimal places as needed.) Use the results from three weeks prior to the newer survey. The interval is a confidence interval. (Round to one decimal place as needed.)