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The state test scores for 12 randomly selected high school seniors are shown on the 1422 1229 982 right. Complete parts (a) through (c) below. 696 724 840 Assume the population is normally distributed. 724 748 546 628 1450 943 . . . (a) Find the sample mean. x= (Round to one decimal place as needed.) (b) Find the sample standard deviation. s = (Round to one decimal place as needed.) (c) Construct a 95% confidence interval for the population mean u. A 95% confidence interval for the population mean is (,). (Round to one decimal place as needed.)A researcher wishes to estimate, with 95% condence, the population proportion of adults who think Congress is doing a good or excellentjob. Her estimate must be accurate within 4% 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 46% 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 = D (Round up to the nearest whole number as needed.) (b) What is the minimum sample size needed using a prior study that found that 46% of the respondents said they think Congress is doing a good or excellent job? n = D (Round up to the nearest whole number as needed.) (c) How do the results from (a) and (b) compare? 0 A. Having an estimate of the population proportion raises the minimum sample size needed. 0 B. Having an estimate of the population proportion has no effect on the minimum sample size needed. 0 C. Having an estimate of the population proportion reduces the minimum sample size needed. A researcher wishes to estimate, with 99% confidence, the population proportion of adults who eat fast food four to six times per week. Her estimate must be accurate within 5% of the population 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 eat fast food four to six times per week. (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 18% of the respondents said they eat fast food four to six times per week? n= (Round up to the nearest whole number as needed.) (c) How do the results from (a) and (b) compare? O A. Having an estimate of the population proportion raises the minimum sample size needed. O B. Having an estimate of the population proportion reduces the minimum sample size needed. O C. Having an estimate of the population proportion has no effect on the minimum sample size needed