Probability Distribution Objective Type Questions and Answers

21 Which of the following statement is not true for an exponential distribution with parameter λ?

A the distribution is completely determined once the value of λ is known

B the area under the curve is equal to one

C the distribution is a two-parameter distribution since the mean and standard deviation are equal

D standard deviation = 1 / λ

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Answer: the distribution is a two-parameter distribution since the mean and standard deviation are equal

22 Indicate which of the statements below does not correctly apply to normal probability distributions:

A they all have the same mean and standard deviation

B for the standard normal distribution µ = 0 and σ = 1

C they are all unimodal (ie: have a single mode)

D they are all symmetrical

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Answer: they all have the same mean and standard deviation

23 Which probability distribution is appropriate for a count of events when the events of interest occur randomly, independently of one another and rarely?

A poisson distribution

B normal distribution

C uniform distribution

D exponential distribution

View Answer

Answer: poisson distribution

24 The mean for the exponential distribution equals the mean for the Poisson distribution only when the former distribution has a mean equal to

A 1.0

B 2.0

C 0.5

D the means of the two distributions can never be equal

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Answer: 1.0

25 In a popular shopping centre, the waiting time for an ABSA ATM machine is found to be uniformly distributed between 1 and 5 minutes. What is the probability of waiting between 2 and 3 minutes to use the ATM?

A 0.40

B 0.25

C 0.50

D None

View Answer

Answer: 0.25

26 What is the area under a conditional Cumulative density function ?

A 1

B Infinity

C Changes with CDF

D 0

View Answer

Answer: 1

27 The expected value of a discrete random variable ‘x’ is given by

A ∑ x P(x)

B P(x)

C ∑ P(x)

D 1

View Answer

Answer: ∑ x P(x)

28 If ‘X’ is a continuous random variable, then the expected value is given by

A ∫ X P(X)

B ∑ x P(x)

C P(X)

D No value such as expected value

View Answer

Answer: ∫ X P(X)

29 Which of the following distributions is suitable to model the length of time that elapses before the first employee passes through the security door of a company?

A uniform

B poisson

C normal

D exponential

View Answer