Question

5a

as part of a quality improvement program, your mail-order company is evaluating the process of filling customer orders. According to company standards, an order is shipped on time if it is sent within two working days of the time it is received. You select an SRS of 234 of the 6,000 orders received in the past month for an audit. The audit reveals that 101 of these orders were shipped on time.

What is the upper endpoint of a 99% confidence interval for p, the population proportion of orders in the last month that were shipped on time?

(Apply the large-sample confidence interval procedure. You will need to calculate z* in Excel, and do not round in your intermediate calculations.)

Express your answer in decimal form to two decimal places of accuracy.

5b

Your company manufacturers electronic thermostats. Each thermostat uses a temperature sensitive switch to turn the heating/cooling system that it controls on or off. Periodically, you inspect a batch of switches from a large shipment of switches to verify quality of the work of your supplier. Let X = number of failures in the sample. Let p = the true proportion of failing switches in the shipment.

Suppose that in an SRS of 118 switches, you find 3 failures.

What is the upper endpoint of a 99% confidence interval for p, the population proportion of failing switches?

(You will need to calculate z* in Excel, and do not round in your intermediate calculations. Use the Wilson Estimate to calculate the interval.)

Express your answer in decimal form to two decimal places of accuracy.

Answer 1