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1. Decide whether the random variable is discrete or continuous. 
a.The number of bottles of water drunk in Florida in August 2008
Discrete 
OK
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b.The number of wasps in the lab test nest
Discrete
OK
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c.The height of sophomores in a required US History class at Ridgemont High in 2008
Continuous
OK
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d.The number of players on the Washington Redskins
Discrete
OK
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e.The speed of cars starting in the Darlington 500 in 2008
Continuous
OK
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2. Decide whether the distribution is a probability distribution. If it is not a probability distribution, identify the property that is not satisfied. 
x P(x)
1 0.200
2 0.238
3 0.245
4 0.307 
No it is not a probability distribution. It does not equal 1.
0.200 + 0.238 + 0.245 + 0.307 = 0.99 
OK
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Section 4.2: Binomial Probability 

4. In a local college, 60% of the math majors are women. Fifteen math majors are chosen at random. (1 points each) 
a. What is the probability that exactly 6 are women?
P(x=6) = 15C6(0.6)^6*(0.4)^9 = binompdf(15,0.6,6)= 0.0612
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b. What is the probability that 5 or less women are selected?
P(0&lt;= x &lt;= 5) = binomcdf(16,0.6,5) = 0.0338 
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c. What is the probability that 10 women are selected?
P(x=10) = binompdf(15,0.6,10) = 0.1859
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d. Find the mean 
mean = np = 15*0.6 = 9
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e. Find the variance  
variance = npq = 9*0.4 = 3.6
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5. A multiple choice test has 20 questions with each having 4 possible answers with one correct. Assume a student randomly guesses the answer to every question. (2.5 points each) 
a. What is the probability of getting exactly 11 correct answers?
binompdf(20,0.25,11) = 0.0030
b. What is the probability of getting less than 9 correct answers?
binomcdf(20,0.25,8) = 0.9591
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Cheers,
Stan H.

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