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Exam 2 80 MINUTES Multiple Choice (2 points each)
Identgs the letter qfthe choice that beat corruption: the statement or answers the question. I. Msume z is the standard nomtal random variable. lfthe atea between zero and a is .4115, then the :. value is a. 2.70 e. 1.00
b. L35 :1 0.207? 2. Assume 2 is the standard normal random variable. lftltc area to the tight of z is .8413, then .7 is
a. 1.0 c. 2.0
b. [.0 d. 2.0 3. Ausumc z is a standard nomal random variable, the Prom2.54 < z < 2.54) aqunls
a. 0.4945 0. 0.5400
it. 0.0U00 d. 0.9890 4. Assume a is It standard normal random variable. the Probﬂdz < z < 3.05] equals
a. 0.4989 c. 0.0091
[3. 0.9887 (1. 0.7300 Problems 5. According to gwemmo‘nt data. 27% of American children Imdet the age of 6 live in households with incomes less than the ofﬁcial poverty level. A study of learning in early childhood chooses a simple random sample of 300
children. A. What is the probability that more than 20% of the sample are from poxmy households? [5 points) B. Was is the probability that more than 30% nfthe sample are ﬁom poverty households? (5 points} 6. I'm: quality conttol department emplqs four technicians during the day shiﬁ. mete are an avetme of l S
shutdowns in a week. Listed below are the number of times tench technician {an average) instructs the production foreman to shutdown the manufacturing process in a given week. You can use this information to calculate the
probability that any technician orders shutdowns. Technician Shutoms
Taylor 4
Hurley 3
Don S .
Sam 3 ' A. lfwe know there were l5 shutdowns last week. What is the probability that only 3 west: ordered by Don'!
(6)7013!!!) B. in a week with 25 shutdowns= what is the probability that Hurley ordered 8 of the shutdown? (ti points) Name: ID: A 'J'. The sums of students on the SA'J' college entrance examination in at teemt year had the normal distribution with
mean 18.6 and standard deviation 5.9. A. What is the prnhahiiity that a single student randomly chosen from all those taking the neat acorns no more than
a 21'? (5 points} B. From a random sample of 50 students who took the test. what is the probability that the mean score ol'these
students is less than 20? (5 points} 8. The in duatry standards suggest that l U pcrccnt of new vehicles require warranty service within the ﬁrst year.
Jones Nissan in Sumter. South Carolina. sold 12 Nissans writ«day. A. what is the probaln'lit}I that none of these vehicles requires warranty service? {Jpoinrs} B. What is the probability exactly one of these vehicles requires warranty service? (4 points} (1. Determine the probability that more than three of the vehicles require warranty service? (7 paints]
i). What is the average number of vehicles that will require warranty service? (5 polars} E. Compute the standard deviation of this probability dim'ihution. {5 points) 9. Customers experiencing technical difﬁculty with their Internet eahle hookup may call an 800 number for technical
support. lttrkes the technician between 30 seconds and 10 minutes to resolve the pmblem. The distribution of
this Support time follows the uniform distribution. {Make sure you indicate the units for each of‘ your answers] A. What is the mean time to resolve the problem? [4 points)
13. What is the Standard deviation for problem resolution times? (4 mints)
C. What percent of the problems take more than 5 minutes to resolve? {1 points) D. Suppose we wish to find the middle :10 percent of the problemsolving times. What are the end points of this
rmge? (5 points) 10'. The Scrapper Elevation: Company has 20 sales representatives who sell their product thmtghmtl the United Sate:
and Canada. The number of units sold by each representative is Iistctl below. Assume time sales ﬁgures to in the
population values [and assume that this data is distributed normally}. 23233424322?34533335 A. Compuae the mean of this distribution. Groin”) B. The standard deviation for the above population is 1.47. Lfyou take samples of S representatives (randomly),
what: will be your sampling distribution of the mean? [Write [his with the correct notationf] (.5 points) 0. What is the Whahilily that the mean of any 5 randomly selected sales ﬁgures will bl: less than 31’ {6:201:13} In! ...
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 Spring '07
 Felkey

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