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Sample size and confidence interval

(21) The U.S. Commission of Crime wishes to estimate the fraction of crimes related to firearms in an area with one of the highest crime rates in the country. The commission randomly selects 600 files of recently committed crimes in an area and finds 380 in which a firearm was reportedly used. Construct the 95% confidence intervals for p , the true population proportion of crimes in the area in which some type of firearm was reportedly used.

(22) A pollster wishes to estimate the proportion of United States voters who favor capital punishment. Find the minimum sample size "n" that is needed to estimate p, the population proportion of voters who favor capital punishment. The pollster wants to be 90% confident that the sample proportion will not differ from the true proportion by more than 4%.

Solution Summary

This solution gives the step by step method for computing sample size and confidence interval.