Confidence interval for a population proportion
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3.a) Consider the population of Wisconsin licensed drivers aged 20 or younger. A random sample of size 363 from this population is obtained. Fifty three (53) of these people state that they drink alcoholic beverages 'several times a week'. Find a 98% confidence interval for the proportion in the entire population who drink 'several times a week'.
3.b) A bank believes that approximately 25% of its checking account customers have used at least one other service provided by the bank during the last six months. How large a sample will be needed to estimate the true proportion to within 0.10 at the 99% level of confidence?
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This solution shows step-by-step how to construct and interpret a confidence interval for a population proportion.
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Level of Confidence
Consider the population of Wisconsin licensed drivers aged 20 or younger. A random sample of size 363 from this population is obtained. Fifty three (53) of these people state that they drink alcoholic beverages "several times a week". Find a 98% confidence interval for the proportion in the entire population who drink "several times a week".
This is a 98% confidence interval for , the population proportion.
The formula for a confidence interval for is:
The values of the variables ...
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