Reading 9: Common Probability Distributions LOS a习题精选

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发表于 2010-4-15 22:37 | 只看该作者

Which of the following is least likely a probability distribution?

A)	Zeta Corp.: P(dividend increases) = 0.60, P(dividend decreases) = 0.30.

B)	Roll an irregular die: p(1) = p(2) = p(3) = p(4) = 0.2 and p(5) = p(6) = 0.1.

C)	Flip a coin: P(H) = P(T) = 0.5.

All the probabilities must be listed. In the case of Zeta Corp. the probabilities do not sum to one.

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发表于 2010-4-15 22:38 | 只看该作者

Which of the following statements about probability distributions is least accurate?

A)	A discrete random variable is a variable that can assume only certain clearly separated values resulting from a count of some set of items.

B)	The skewness of a normal distribution is zero.

C)	A binomial probability distribution is an example of a continuous probability distribution.

The binomial probability distribution is an example of a discrete probability distribution. There are only two possible outcomes of each trial and the outcomes are mutually exclusive. For example, in a coin toss the outcome is either heads or tails.

The other responses are both correct definitions.

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4^#

发表于 2010-4-15 22:38 | 只看该作者

Which of the following statements about probability distributions is least accurate?

A)	A probability distribution is, by definition, normally distributed.

B)	In a binomial distribution each observation has only two possible outcomes that are mutually exclusive.

C)	A probability distribution includes a listing of all the possible outcomes of an experiment.

Probabilities must be zero or positive, but a probability distribution is not necessarily normally distributed. Binomial distributions are either successes or failures.

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5^#

发表于 2010-4-15 22:38 | 只看该作者

A probability distribution is least likely to:

A)	contain all the possible outcomes.

B)	give the probability that the distribution is realistic.

C)	have only non-negative probabilities.

The probability distribution may or may not reflect reality. But the probability distribution must list all possible outcomes, and probabilities can only have non-negative values.

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发表于 2010-4-15 22:39 | 只看该作者

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?

0.001.

0.200.

0.167.

The probability of a value being rolled is 1/6 regardless of the previous value rolled.

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发表于 2010-4-15 22:39 | 只看该作者

The number of ships in the harbor is an example of what kind of variable?

A)	Indiscrete.

B)	Continuous.

Discrete.

A discrete variable is one that is represented by finite units.

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8^#

发表于 2010-4-15 22:39 | 只看该作者

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.

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.

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发表于 2010-4-15 22:40 | 只看该作者

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.

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.

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10^#

发表于 2010-4-27 15:52 | 只看该作者