Exam 9: Random Variables and Statistics

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In a large on-the-job training program, half of the participants are female and half are male. In a random sample of 6 participants, what is the probability that an investigator will draw at least 2 females Round your answer to four decimal places.

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If we model after-tax household income with a normal distribution, then the figures of a 1995 study imply the information in the following table. Assume that the distribution of incomes in each country is normal, and round all percentages to the nearest whole number. What percentage of Sweden households had an income of $50,000 or more Country U.S. Canada Switzerland Germany Sweden Mean household income \ 38,000 \ 35,000 \ 39,000 \ 34,000 \ 32,000 Standard deviation \ 21,000 \ 17,000 \ 16,000 \ 14,000 \ 11,000

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Calculate the expected value of X for the given probability distribution. x 1 2 3 4 P(X=x) 0.6 0.1 0.1 0.2

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Compute the (sample) variance and the standard deviation for the data. ​ 2.1,5.4,4.6,4.1,0.1,0.12.1 , - 5.4,4.6,4.1 , - 0.1 , - 0.1 ​ Please round your answers to two decimal places. ​ s2=s ^ { 2 } = __________ ​ s=s = __________

(Short Answer)
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A random variable has the probability distribution table as shown. Calculate P(x5)P ( x \geq 5 ) . x 1 3 5 7 9 P(X=x) 0.4 0.2 0.1 0.2 ​ P(x5)=P ( x \geq 5 ) = __________

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Calculate the standard deviation of the given random variable X. Please round your answer to two decimal places. Forty-five darts are thrown at a dartboard. The probability of hitting a bull's-eye is 0.4. Let X be the number of bull's-eyes hit.

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Given the data. 4,0,4,4,64,0 , - 4,4,6 Compute the mean.

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You are performing seven independent Bernoulli trials with p=0.7p = 0.7 and q=0.3q = 0.3 . Calculate the probability of two successes. Round your answer to five decimal places if necessary.

(Multiple Choice)
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The following is a sample of tow ratings (in pounds) for some popular 2000 model light trucks: ​ 2,000, 2,000, 4,000, 5,000, 6,000, 7,000, 7,000, 7,000, 8,000, 8,000 ​ Compute the mean of the given sample. Round your answer to the nearest whole number. ​ xˉ=\bar { x } = __________ ​ Compute the standard deviation of the given sample. Round your answer to the nearest whole number. ​ s=s = __________ ​ Assuming the distribution of tow ratings for all popular light trucks is symmetric and bell-shaped, 68 percent of all light trucks have tow ratings between __________ and __________. Please, use the rounded value for the standard deviation here. ​ Find the percentage of scores in the sample that fall in this range. ​ __________%

(Short Answer)
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The probability that a randomly selected pound of beef is purchased by McDonald's is 0.09. Ten pounds of beef are chosen at random. What is the probability that exactly two of them are purchased by McDonald's Round your answer to four decimal places.

(Multiple Choice)
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Calculate the standard deviation of X for the probability distribution. Please round your answer to the nearest whole number, if necessary. x -5 -2 0 3 6 9 P(X=x) 0.2 0.3 0.2 0.1 0 0.2 ​ σ=\sigma = __________

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According to classical mechanics, the energy of an electron in a hydrogen atom can assume any positive value. ​V - the energy of an electron in a hydrogen atom. ​ Classify the random variable V as finite, discrete infinite, or continuous.

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If we model after-tax household income by a normal distribution, then the figures of a 1995 study imply the information in the following table. Assume that the distribution of incomes in each country is bell-shaped and symmetric. If we define a "rich" household as one whose after-tax income is at least 1.3 standard deviations above the mean, find the household income of a rich family in Germany. Country U.S. Canada Switzerland Germany Sweden Mean Household Income \ 38,000 \ 35,000 \ 39,000 \ 34,000 \ 32,000 Standard Deviation \ 21,000 \ 17,000 \ 16,000 \ 14,000 \ 11,000 ​ The household income of a rich family in Germany is __________ or __________ (more or less).

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Calculate the standard deviation of X for the probability distribution. Please round your answer to two decimal places, if necessary. x -5 -2 0 3 6 10 P(X=x) 0.2 0.3 0.2 0.1 0 0.2

(Multiple Choice)
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The following table shows the average percentage increase in the price of a house from 1980 to 2001 in 9 regions of the U.S. New England 300 Pacific 225 Middle Atlantic 225 South Atlantic 175 Mountain 175 West North Central 100 West South Central 75 East North Central 175 East South Central 100 Let X be the percentage increase in the price of a house in a randomly selected region. What is the probability that, in a randomly selected region, the percentage increase in the cost of a house exceeded 200%

(Multiple Choice)
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You are performing seven independent Bernoulli trials with p=0.1p = 0.1 and q=0.9q = 0.9 . Calculate the probability of no successes. Round your answer to four decimal places.

(Short Answer)
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Find the expected value of the following probability distribution. x 3 9 12 16 P(X=x) 0.3 0.5 0.1 0.1

(Multiple Choice)
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If we model after-tax household income by a normal distribution, then the figures of a 1995 study imply the information in the following table. Assume that the distribution of incomes in each country is bell-shaped and symmetric. Find the percentage of swiss families which earned an after-tax income of $71,000 or more. Round your answer to one decimal place if necessary. Country U.S. Canada Switzerland Germany Sweden Mean Household Income \ 38,000 \ 35,000 \ 39,000 \ 34,000 \ 32,000 Standard Deviation \ 21,000 \ 17,000 \ 16,000 \ 14,000 \ 11,000 ​ The percentage is __________%.

(Short Answer)
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Calculate the standard deviation of X for the probability distribution. x 1 2 3 4 P(X=x) 0.2 0.3 0.3 0.2 Round your answer to two decimal places if necessary.

(Multiple Choice)
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The table shows crashworthiness ratings for several categories of motor vehicles. Take X as the crash-test rating of a small car, ​Y as the crash-test rating for a small SUV, and so on, as shown in the table. Overall Frontal Crash Test Rating Number Tested 3 (Good) (Acceptable) 1 (Marginal) 0 (Poor) Small Cars X 16 1 11 2 2 Small SUVs Y 10 1 4 4 1 Medium SUVs Z 15 3 5 3 4 Passenger Vans U 14 3 0 3 8 Midsize Cars V 16 3 5 0 8 Large Cars W 19 9 5 3 2 ​ Compute the probability distribution for X. x 3 2 1 0 P(X=x)

(Short Answer)
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