Quiz 4 fa 06 KEY

# Quiz 4 fa 06 KEY - * d. .5628 e. .7852 f. .9999 1 3. A...

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ECON 2843 Name KEY Quiz 4 Fall 2006 ID # Students must show all work on problems that involve calculation. 1. A study of commercial airline flights of under 2 hours showed that the flights are approximately Gaussian (i.e., Normally) distributed with an average late time for a flight of 2.48 minutes and a standard deviation of 12 minutes. If a sample of 28 flights is taken, then what is the probability that the sample variance will be greater than 68.69? .99 2. The highway department is interested in the proportion of vehicles on Interstate 35 between the hours of midnight and 5:00 a.m. that are 18-wheel tractor trailers. It has been found that this proportion is about 26.63%. If a random sample of 288 vehicles is taken, then what is the probability that between 27 percent and 33 percent of these vehicles will be tractor trailers? Circle the correct answer but also show your work. a. .0091 b. .3461 c. .4372

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Unformatted text preview: * d. .5628 e. .7852 f. .9999 1 3. A manufacturing plant produces steel rods, which follow a Gaussian distribution with a mean of 45 centimeters and a standard deviation of 5 centimeters. A random sample of 15 bills was taken. Find the probability that the sample standard deviation will be less than 6.5 cm. Probability = .95 4. Refer to question 3. The probability is 2.5% that the sample standard deviation will be less than what number? 3.17 5. a. If the expected value of the estimator a is equal to the value of the parameter , then a is said to be unbiased . b. If an estimator a is the most efficient of all the estimators under consideration, then a has a smaller variance than do all of the rest of the estimators. c. If for any positive number , P[ a- &lt; ] 1 as the sample size becomes very large, then a is said to be consistent . 2...
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## Quiz 4 fa 06 KEY - * d. .5628 e. .7852 f. .9999 1 3. A...

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