Question

1) You measure 30 textbooks' weights, and find they have a mean weight of 70 ounces. Assume the population standard deviation is 8.7 ounces. Based on this, construct a 90% confidence interval for the true population mean textbook weight. Give as your answer as decimals, to two places.

2) In 2011 the U.S. Department of Transportation reported with 95% confidence that the average length of a motor vehicle trip in the United States was 9.72 miles with a margin or error of 0.22 miles.

With 95% confidence the authors of the report are claiming that the true average length of a motor vehicle trip in the United States is between ? and ? miles.

The level of confidence for this estimate is ?

3) In a survey, 11 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $50 and standard deviation of $14. Construct a confidence interval at a 90% confidence level.

4) If n=14, ¯xx¯(x-bar)=34, and s=17, construct a confidence interval at a 98% confidence level. Assume the data came from a normally distributed population.

5) Out of 200 people sampled, 132 had kids. Based on this, construct a 95% confidence interval for the true population proportion of people with kids.

Answer 1

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