Questions
21
Which of the following statement is not true for an exponential distribution with parameter λ?
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:
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?
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
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?
Answer: 0.25
26
What is the area under a conditional Cumulative density function ?
Answer: 1
27
The expected value of a discrete random variable ‘x’ is given by
Answer: ∑ x P(x)
28
If ‘X’ is a continuous random variable, then the expected value is given by
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?
Answer: exponential
