# 95% Confidence Interval for the population proportion

The Friday after Thanksgiving is the biggest shopping day of the year. You are interested in the number of people who claim to have finished their Christmas shopping at the end of this weekend. On Monday, you take a random sample of people by standing at a toll booth at 7:00 a.m. and asking every third commuter if he or she has finished Christmas shopping. Based on the last year's data, you expect approximately 10% to claim completion of Christmas shopping. How many commuters must you sample of a 95% interval estimate to have a margin of error of +3%.

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Solution. The margin of error ME=3%=0.03, phat=10%=010. For a 95% confidence level, ...

#### Solution Summary

In this solution, it consists of detailed steps of finding a 95% confidence interval for the population proportion.