A researcher found that 85% of customers who make purchase at a department store are pleased with the store customer ...

  

3. (TCO 5) A researcher found that 85% of customers who make purchase at a department store are pleased with the store customer service. We asked 20 customers whether or not they are please with the store customer service.

(a) Is this a binomial experiment? Explain how you know.
(b) Use the correct formula to find the probability that, out of 20 customers, exactly 12 of them are pleased with the store customer service. Show your calculations or explain how you found the probability. (Points : 20)

7. (TCO 7) A company’s CEO wanted to estimate the percentage of defective product per shipment. In a sample containing 400 products, he found 25 defective products.
(a) Find a 95% confidence interval for the true proportion of defective product. Show your calculations and/or explain the process used to obtain the interval.
(b) Interpret this confidence interval and write a sentence that explains it. (Points : 20)