1. Length of Growing Seasons The growing seasons for a random sample of 31 U.S. cities were recorded, yielding a sample mean of 197.2 days and the population standard deviation of 50.8 days. Estimate the true population mean of the growing season with 96% confidence. Use a graphing calculator and round the answers to one decimal place.

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2. Overtime Hours Worked A random sample of 16 registered nurses in a large hospital showed that they worked on average 44.3 hours per week. The standard deviation of the sample was 2.3. Estimate the mean of the population with 95% confidence. Assume the variable is normally distributed. Round intermediate answers to at least three decimal places. Round your final answers to one decimal place.

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3. Weights of Elephants A sample of 9 adult elephants had an average weight of 12,609 pounds. The standard deviation for the sample was 24 pounds. Find the 95% confidence interval of the population mean for the weights of adult elephants. Assume the variable is normally distributed. Round intermediate answers to at least three decimal places. Round your final answers to the nearest whole number.

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4. Work Time Lost due to Accidents At a large company, the Director of Research found that the average work time lost by employees due to accidents was 103 hours per year. She used a random sample of 22 employees. The standard deviation of the sample was 5.3 hours. Estimate the population mean for the number of hours lost due to accidents for the company, using a 90% confidence interval. Assume the variable is normally distributed. Round intermediate answers to at least three decimal places. Round your final answers to the nearest whole number.

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5. Social Networking Sites A recent survey of 6 social networking sites has a mean of 15.37 million visitors for a specific month. The standard deviation was 3.6 million. Find the 80% confidence interval of the true mean. Assume the variable is normally distributed. Round your answers to at least two decimal places.

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6. Travel to Outer Space A CBS News/New York Times poll found that 329 out of 763 randomly selected adults said they would travel to outer space in their lifetime, given the chance. Estimate the true proportion of adults who would like to travel to outer space with 97% accuracy. Round your answers to at least three decimal places.

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7. Belief in Haunted Places A random sample of 330 college students were asked if they believed that places could be haunted, and 132 responded yes. Estimate the true proportion of college students who believe in the possibility of haunted places with 95% confidence. According to Time magazine, 37% of Americans believe that places can be haunted. Round intermediate and final answers to at least three decimal places.

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8. Manual Transmission Automobiles In a recent year, 6% of cars sold had a manual transmission. A random sample of college students who owned cars revealed the following: out of 131 cars, 27 had manual transmissions. Estimate the proportion of college students who drive cars with manual transmissions with 95% confidence. Round intermediate and final answers to at least three decimal places.

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9. Cyber Monday Shopping A survey of 1050 U.S. adults found that 32% of people said that they would get no work done on Cyber Monday since they would spend all day shopping online. Find the 99% confidence interval of the true proportion. Round intermediate answers to at least five decimal places. Round your final answers to at least three decimal places.

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10. Lifetimes of Wristwatches A random sample of the lifetimes of 25 inexpensive wristwatches has a standard deviation of 4.2 months. Assume the variable is normally distributed. Use the chi-square distribution table to find any chi-square values to three decimal places. Round your final answers to one decimal place.

Find the 95% confidence intervals for the variance and standard deviation.

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11. A study of life expectancy showed that a random sample of 6 states had a standard deviation of 1.0 deaths per year. Find the 98% confidence intervals of the variance and standard deviation. Assume the variable is normally distributed. Use the chi-square distribution table to find any chi-square values to three decimal places. Round your final answers to one decimal place.

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12. Cost of an OperationA medical researcher surveyed 11hospitals and found that the standard deviation for the cost for removing a person's gall bladder was $ 57.Assume the variable is normally distributed. Based on this, find the 95%confidence intervals of the population variance and standard deviation. Round the answers to two decimal places.

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