MyPhone Manufacturing makes smart phones. As part of the company’s quality efforts, the company wishes to estimate the mean number of days the phone is used before repair is needed. A pilot sample of 30 phones indicates a sample standard deviation of 200 days. The company wishes its estimate to have a margin of error of no more than 20 days with a confidence level of 95%. a. Given this information, how many additional phones should be sampled?  b. The pilot study was initiated because of the costs involved in sampling. Each sampled observation costs approximately $20 to obtain. Originally, it was thought that the population’s standard deviation may be as large as 300 days. Determine the amount of money saved by obtaining the pilot sample

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10. MyPhone Manufacturing makes smart phones. As part of the company’s quality efforts, the company wishes to estimate the mean number of days the phone is used before repair is needed. A pilot sample of 30 phones indicates a sample standard deviation of 200 days. The company wishes its estimate to have a margin of error of no more than 20 days with a confidence level of 95%.

a. Given this information, how many additional phones should be sampled? 

b. The pilot study was initiated because of the costs involved in sampling. Each sampled observation costs approximately $20 to obtain. Originally, it was thought that the population’s standard deviation may be as large as 300 days. Determine the amount of money saved by obtaining the pilot sample. 

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