Quiz 4 fa 05 KEY

# Quiz 4 fa 05 KEY - normal distribution with standard...

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ECON 2843 Name KEY Quiz 4 Fall 2005 ID # Students must show all work on problems that involve calculation. 1. It is estimated that total annual running costs of all automobiles of a particular model year follow a normal distribution with standard deviation \$1,400. A random sample of twenty- five of these automobiles is taken. The probability is 99% that the sample variance is less than what number? 3,510,033.333 2. A retail chain has 1,200 stores in the United States. In 192 of these stores, shoplifting has increased by more than 5 % in the past year. A random sample of 100 of these stores is selected. Using the finite population correction factor, what is the probability that the sample proportion is between 10 % and 15 %? Circle the correct answer but also show your work. a. .2800 b. .3461 * c. .3897 d. .5000 e. .6103 f. .9564 1

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3. In a large city it was found that summer electricity bills for single-family homes followed a
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Unformatted text preview: normal distribution with standard deviation \$84. A random sample of 30 bills was taken. Find the probability that the sample standard deviation is greater than \$62.491. Probability = .975 4. Refer to question 3. Find the probability that the sample variance will exceed the population variance by more than 2,455. Circle the correct answer but also show your work. a. .01 b. .05 c. .10 * d. .90 e. .99 f. approximately 1 5. a. If the expected value of the estimator a θ 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 ε , P[ │ a n- │ < ε ] → 1 as the sample size becomes very large, then a is said to be consistent . 2...
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Quiz 4 fa 05 KEY - normal distribution with standard...

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