Large Sample Estimation

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A random sample of 250 youth between the ages of 8 and 18 showed that 170 of them had a TV in their bedroom. Estimate the proportion of all 8 to 18-year-olds who have a TV in their bedroom and calculate the margin of error.

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A pediatrician randomly selected 50 six-month-old boys from her practice's database and recorded an average weight of 8.0 kg with a standard deviation of 0.30 kg. Find a 95% confidence interval for the average weight of all six-month-old boys.

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A survey is designed to estimate the proportion of SUVs being driven in the state of California. A random sample of 500 registrations are selected from a Department of Motor Vehicles database, and 68 are classified as SUVs. Use a 99% confidence interval to estimate the proportion of SUVs in California.

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An entomologist wishes to estimate the average development time of the citrus red mite, a small spider-like insect that causes damage to leaves and fruit, correct within 0.5 day. From previous experiments, it is known that σ is approximately 4 days. How large a sample should the entomologist take to be 95% confident to her estimate?

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