Schadek Silkscreen Printing, Inc. buys plastic cups to print logotypes of sports events, graduations, birthdays and other special events. The owner, Zack Schadek, received an important order or mailing from a customer this morning. To make sure of the quality of the order or mailing, he selected a chance sample of 300 cups and it discovered 15 defective units.

a) Which is the estimated or dear proportion of defective cups in the population?

b) Develop a confidence interval of 95% for the proportion of defective cups.

c) Zack has an agreement with his provider of whom he is going to return the lots in those who exist 10% or more of defective units. Must he return this lot? Explain his decision.