MAS1302: General Feedback on Assignment 2

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MAS1302 General Feedback on Assignment 2

• Part A (computer questions)
• As with Assignment 1, this was generally well
  done by those who made a serious effort.

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Part A Computer Project

• General comments
• Graphs when asked to put a graph into your
  solutions, make sure you sort out labels for the
  axes, and a title.
• If you are asked to describe the shape of a
  distribution from a histogram, do not be too
  distracted by the tallest bar!

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Task 1 (Estimating p)

• 1. This was well done apart from some poor
  labelling of graphs, and misinterpretation of
  histograms which were basically centred about p,
  but whose tallest bar happened not to be at p.
• 2. A number of people didnt make the comparison
  between the plot with 500 points, and plot with
  10,000 points.
• 3. Nevertheless, part 11. in which the accuracy
  of estimators based on 500 points and 10,000
  points was discussed, was done well.

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Task 2 (Birth-death processes)

• Inter-arrival times are Exponential, not Poisson!
  Some people got confused over this.
• End populations could be reported exactly by
  looking at the vectors b1Size etc. in R, and
  reporting the last number! Some people used the
  graphs, and sometimes incorrectly, e.g. reporting
  maximum population size.
• In part 9, you were expected to report the
  proportion of those who survived the first period
  which then went on to survive the second period
  not the proportion of the original 20!
• Part 10, asking whether the Poisson processes
  were homogeneous, was not generally very well
  done a lot of people did not make the link with
  N(t).

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Part B (standard exercises)Question 1.

• (d) (iii) The number of arrivals in a time
  interval is Poisson, not Exponential!
• (e) Make sure you can use Neaves tables for the
  inverse normal cdf!
• (f) When drawing a time line of events, make sure
  you think through whats happening. A number of
  people had the 4th job starting before it had
  arrived!
• (g) Check you understand how to work out what
  will happen to a queue in the long run.

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• Question 2.
• Fairly well done, except for
• (e) The sketch of the utility function this
  should give a good idea of how the utility of
  money changes for this particular scenario!
• (f) (g) Make sure you know how to calculate the
  utility of a gamble!
• (h) The worst answered question! People missed
  the link with the utility function to how they
  thought people behaved.

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Question 3.

• Well done, except for in part (b), some people
  forgot x had to be an integer!