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Quiz 3 sp 05 KEY-1

Quiz 3 sp 05 KEY-1 - taken in order to estimate the mean...

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ECON 2843 Name KEY Quiz 3 Spring 2005 ID # Students must show all work on problems that involve calculation. 1. Suppose that the amount of cosmic radiation to which a person is exposed while flying by jet across the U.S. is a normally distributed random variable with a mean of 4.16 mrem and a variance of .3249 mrem 2 . (mrem = milliroentgen equivalent man). What is the probability that a person will be exposed to more than 4.0 mrem of cosmic radiation on such a flight? Circle the correct answer but also show your work. a. .3121 b. .3897 c. .6368 d. 61.03% * e. 68.79% f. .8632 2. Refer to question 1. What is the probability that a person will be exposed to anywhere from 4.25 to 4.50 mrem? Circle the correct answer but also show your work. 3. Assume that the standard deviation of the amount of money spent in a semester on textbooks by students on a large campus is \$65. A random sample of 225 students is

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Unformatted text preview: taken in order to estimate the mean expenditure for the whole student population. What is the probability that the sample mean differs from the population mean by more than \$8? Circle the correct answer but also show your work. a. Approximately 0 b. .0322 c. .0644 * d. .9356 e. .9678 f. 1.1428 1 4. At a street intersection in Norman, 4% of all drivers run a red light. From the very large number of drivers on a given day, 350 drivers are selected at random. What is the approximate probability that between ten and twenty of the drivers will run the red light? Circle the correct answer but also show your work. a. .0936 b. .1884 c. .3621 d. .8116 * e. .9495 f. between .09 and .64 5. The life of computer speakers is assumed to be normally distributed with a mean of 18 years and a standard deviation of 3.45 years. What is the probability that a speaker will last less than 12 years? .0409 2...
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