# Question: A sample of 200 customers at a supermarket showed that

A sample of 200 customers at a supermarket showed that 28 used a debit card to pay for their purchases.

(a) Find the 95 percent confidence interval for the population proportion.

(b) Why is it OK to assume normality in this case?

(c) What sample size would be needed to estimate the population proportion with 90 percent confidence and an error of ± .03?

(a) Find the 95 percent confidence interval for the population proportion.

(b) Why is it OK to assume normality in this case?

(c) What sample size would be needed to estimate the population proportion with 90 percent confidence and an error of ± .03?

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