Portland State University



Stat243BU Quiz #4 Spring 2015 Students can use a page of note (front and back) prepared by themselves and a calculator. However, class notes and textbooks are not allowed. Each problem is of 5 points worth.NAME: KEY1. The probability that a continuous random variable takes any specific valuea.is equal to zerob.is at least 0.5c.depends on the probability density functiond.is very close to 1.0ANS:A2. In a standard normal distribution, the probability that Z is greater than 0.5 isa.0.5b.equal to 1c.at least 0.5d.1.96ANS:A3. Which of the following is not a characteristic of a normal probability distribution?a.The mean, median, and the mode are equalb.The mean of the distribution can be negative, zero, or positivec.The distribution is symmetricald.The standard deviation must be 1ANS:D4. The probability density function for a uniform distribution ranging between 2 and 6 isa.4b.undefinedc.any positive valued.0.25ANS:D5. Z is a standard normal random variable. The P(-1.96 Z -1.4) equalsa.0.8942b.0.0558c.0.475d.0.4192ANS:B6. X is a normally distributed random variable with a mean of 5 and a variance of 4. The probability that X is greater than 10.52 isa.0.0029b.0.0838c.0.4971d.0.9971ANS:A7. Given that Z is a standard normal random variable, what is the value of Z if the area to the right of Z is 0.0559?a.0.4441b.1.59c.0.0000d.1.50ANS:B8. Given that Z is a standard normal random variable, what is the value of Z if the area to the right of Z is 0.9834?a.0.4834b.-2.13c.+2.13d.zeroANS:B9. Use the normal approximation to the binomial distribution to answer this question. Fifteen percent of all students at a large university are absent on Mondays. If a random sample of 12 names is called on a Monday, what is the probability that four students are absent?a.0.0683b.0.0213c.0.0021d.0.1329ANS:AProblems 10 – 13: The average price of personal computers manufactured by MNM Company is $1,200 with a standard deviation of $220. Furthermore, it is known that the computer prices manufactured by MNM are normally distributed.10. What is the probability that a randomly selected computer will have a price of at least $1,530?a.0.0668b.0.5668c.0.4332d.1.4332ANS:puters with prices of more than $1,750 receive a discount. What percentage of the computers will receive the discount?a.62%b.0.62%c.0.062%d.99.38%ANS:B12.What is the minimum value of the middle 95% of computer prices?a.$1,768.80b.$1,295.80c.$2,400.00d.$768.80ANS:D13.If 513 of the MNM computers were priced at or below $647.80, how many computers were produced by MNM?a.185,500b.85,500c.513,000d.not enough information is provided to answer this questionANS:B ................
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