# 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?

**View Solution:**## Answer to relevant Questions

“Smokers are much more likely to speed, run red lights, and get involved in car accidents than nonsmokers.” (a) Can you think of reasons why this statement might be misleading? (b) Can you suggest a causal link between ...“Lacrosse helmets are not needed,” said Tom. “None of the guys on my team have ever had head injuries.” Is there a fallacy in Tom’s reasoning? Explain. (a) How much statistics does a student need in your chosen field of study? Why not more? Why not less? (b) How can you tell when the point has been reached where you should call for an expert statistician? List some costs ...Would you use a sample or a census to measure each of the following? Why? a. The model years of the cars driven by each of your five closest friends. b. The model years of the cars driven by each student in your statistics ...Which statement is incorrect? Explain. a. If p = .50 and n = 100, the estimated standard error of the sample proportion is .05. b. In a sample size calculation for estimating , it is conservative to assume π = .50. c. If n ...Post your question