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T-Printing Inc. purchases plastic cups on which to print logos for sporting even

ID: 3157529 • Letter: T

Question

T-Printing Inc. purchases plastic cups on which to print logos for sporting events, proms, birthdays, and other special occasions. The owner received a large shipment this morning. To ensure the quality of the shipment, he selected a random sample of 300 cups. He found 16 to be defective. What is the estimated proportion defective in the population? Develop a 95% confidence interval for the proportion defective. The owner has an agreement with his supplier that he is to return lots that are 8% or more defective. Should he return this lot? Explain your decision.

Explanation / Answer

a)

P = 16 / 300 = 0.053

b)

alpha / 2 = 0.025 Z= 1.96

0.053 +/- 1.96 * SRQT ( [ 0.053*0.947 ] / 300 )

0.053 +/- 0.02535

0.02765 < P < 0.07835

2.765% < P < 7.835%

c)

since in the interval is not 8% we conclude that He should not return the lot because we are 95% that the proportion of defective in the population is between 2.76% and 7.83%