Question

a. An analyst from an energy research institute in California wishes to estimate the 95% confidence interval for the average price of unleaded gasoline in the state. In particular, she does not want the sample mean to deviate from the population mean by more than $0.06. What is the minimum number of gas stations that she should include in her sample if she uses the standard deviation estimate of $0.35, as reported in the popular press? Round intermediate calculations to at least 4 decimal places and "z" value to 3 decimal places. Round up your answer to the nearest whole number.)

Minimum # of Gas Stations -

b. In the planning stage, a sample proportion is estimated as pˆp^ = 72/80 = 0.90. Use this information to compute the minimum sample size n required to estimate p with 95% confidence if the desired margin of error E = 0.05. What happens to n if you decide to estimate pwith 90% confidence? Round intermediate calculations to at least 4 decimal places and "z" value to 3 decimal places. Round up your answers to the nearest whole number.)  

c. In a recent poll of 400 homeowners in the United States, one in four homeowners reports having a home equity loan that he or she is currently paying off. Using a confidence coefficient of 0.90, derive the interval estimate for the proportion of all homeowners in the United States that hold a home equity loan.Round intermediate calculations to at least 4 decimal places. Round "z" value and final answers to 3 decimal places.)

Answer 1