Q6. A dealer in a casino has rolled a five on a single die three times in a row. What is the probability of her rolling another five on the next roll, assuming it is a fair die?
A) 0.167.
B) 0.001.
C) 0.200.
Correct answer is A)
The probability of a value being rolled is 1/6 regardless of the previous value rolled.
Q7. The number of ships in the harbor is an example of what kind of variable?
A) Discrete.
B) Indiscrete.
C) Continuous.
Correct answer is A)
A discrete variable is one that is represented by finite units.
Q8. Which of the following is a discrete random variable?
A) The realized return on a corporate bond.
B) The amount of time between two successive stock trades.
C) The number of advancing stocks in the DJIA in a day.
Correct answer is C)
Since the DJIA consists of only 30 stocks, the answer associated with it would be a discrete random variable. Random variables measuring time, rates of return and weight will be continuous.
Q9. Which of the following statements about probability distributions is most accurate?
A) A discrete uniform random variable has varying probabilities for each outcome that total to one.
B) A binomial distribution counts the number of successes that occur in a fixed number of independent trials that have mutually exclusive (i.e. yes or no) outcomes.
C) A continuous uniform distribution has a lower limit but no upper limit.
Correct answer is B)
Binomial probability distributions give the result of a single outcome and are used to study discrete random variables where you want to know the probability that an exact event will happen. A continuous uniform distribution has both an upper and a lower limit. A discrete uniform random variable has equal probabilities for each outcome. | 
发表于 2009-6-7 13:16
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