QBUS5002: Quantitative Methods for Accounting
Assignment (Part 1)
2. Event Management. An events manager is planning to hold a festival in Sydney for the entire month
of July in 2022 and asks the weather expert for some advice on the likely number of days it could
rain which could impact the number of people attending the festival. The weather expert notes
that historically 21% of all days are rainy days for the month of July in Sydney. The weather
expert believes that the number of rainy days in July in 2022 could be modelled with a Binomial
(a) (2 points) Discuss the requirements of the Binomial distribution and whether you feel it is
appropriate in the current scenario.
(b) (3 points) Assuming the Binomial distribution is appropriate for modelling the number of rainy
days in July 2022, determine the probabilities of the following:
i Exactly 8 rainy days in July next year
ii Less than 9 rainy days of rain in July next year
(c) (2 points) What is the expected number of rainy days in Sydney during July next year and
what is the variance of the number of rainy days?
The events manager is also concerned about the possibility of serious transport disruptions to
the Sydney rail network, which can seriously impact the number of people able to attend the
festival. The events manager contacts Transport for NSW who inform her that serious disruptions typically occur at a rate of 1 per 40 weekdays. On weekends, disruptions are less frequent
occurring at a rate of 1 per 80 days.
(d) (2 points) The events manager believes the number of disruptions on weekdays and weekends
can be separately modelled as Poisson random variables. Discuss whether you feel the choice
of the Poisson distribution is appropriate for modelling the number of disruptions on either
weekdays or weekends.
(e) (3 points) Assuming the Poisson distribution is appropriate for modelling these disruptions,
determine the probabilities of the following:
i No more than 4 transport disruptions on weekdays during July next year
ii Zero transport disruptions on weekends during July next year
(f) (2 points) Find the mean and variance for the number of weekday disruptions in July next year.
(g) (2 points) Find the mean and variance for the number of weekend disruptions in July next year.
(h) (4 points) The events manager believes the level of profit from the festival is linked to both the
amount of rain and the number of transport disruptions in the following way:
P = 500 − 24R − 36D − 40E
where P is the amount of profit measured in thousands of dollars, R is the number of rainy days,
D is the number of weekday transport disruptions, and E is the number of weekend transport
disruptions all in July next year. Calculate the expected profit for the festival, as well as the
standard deviation of profit, stating any required assumptions.
3. Website Speed. The speed at which you can log into a website through a smartphone is an important
quality characteristic of that website. In a recent test, the mean time to log into the INFORMS
OR/MS Tomorrow website was 6.734 seconds. Suppose that the download time is normally distributed, with a standard deviation of 2.7 seconds. What is the probability that a download time
(a) (2 points) less than 2 seconds?
(b) (2 points) between 1.8 and 2.4 seconds?
(c) (2 points) 99% of the download times are slower (higher) than how many seconds?
(d) (2 points) 95% of the download times are between what two values, symmetrically distributed
around the mean?
(e) (1 point) Suppose the download times are uniformly distributed between 1 to 13 seconds. What
is your answer to 3(b)?
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