Confidence_Interval

Confidence_Interval - Confidence Interval for a Population...

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Confidence Interval for a Population Mean 1. A physician wanted to estimate the mean length of time μ that a patient had to wait to see him after arriving at the office. A random sample of 36 patients showed a mean waiting time of 23.4 minutes and a standard deviation of 7.2 minutes. Find a 96% confidence interval for . 2. The owner of a small computer company wished to estimate the mean download rate for the company's update to one of its programs. Forty-nine downloads gave a mean rate of 3.1 and a standard deviation of 1.6 kilobits per second. Find a 98% confidence interval for . 3. Barbara wanted to estimate the mean connection time to the Internet. She connected 25 times with a mean of 42 and a standard deviation of 5.2 minutes. Find a 90% confidence interval for . 4. A study was done to estimate the mean annual growth in a population of Conuspennaceus trees in Hawaii. For those with an initial size of 2.41-2.60 centimeters, a sample of size 12 yielded a mean annual growth of .72 centimeter and a standard deviation of .31 centimeter. Find a 90% confidence interval for the population mean of annual growth (of those trees with an initial size of 2.41-2.60 centimeters). 5. 16 pieces of a plastic are randomly selected, and the breaking strength of each piece is recorded in pounds per square inch. Suppose that: X = 26 and s = 1.5 pounds per square inch. Find a 99% confidence interval for the mean breaking strength . If you were to obtain 200 those 99% confidence intervals for the mean breaking strength, about how many can be expected to contain ? 6. A city assessor wished to estimate the mean income per household. The previous mean
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This note was uploaded on 12/11/2011 for the course STA 3123 taught by Professor Staff during the Fall '08 term at FIU.

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Confidence_Interval - Confidence Interval for a Population...

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