SF2942: Statistics for reexam Dec 2016
General information
First some general information regarding the exam.
Partial credits were assigned according to
Problem 1: a - 2, b - 4, c - 4,
Problem 2: a - 7, b - 3,
Problem 3: a - 6, b - 4,
Probem 5: a - 4, b - 6.
In problem 2, strictly speaking there are no arbitrage opportunities, even though we have a negative interest rate for the first cash flow time. However, those who have argued that one could keep the money in one’s pocket - that is, use a contract with discount factor one for any time - have been awarded full credit. Note however that since no such bond/contract is available in the given market, there is a set of discount factors consistent with the prices and thus no arbitrage.
In problem 3, you can be awarded full credit if you use the (erroneous) face value 250 for Bond C. The requirement is that you have commented on the then strange behavior of the discount factors - they do not follow the pattern we know discount factors / interest rates to (typically) have.
Lastly, for problem 4, what is needed for full credit is (i) compute the joint distribution of the bonds (or associated indicators if you prefer), (ii) formulate the maximization problem using the given utility function, and (iii) write down some form of the optimality conditions / equation system that will give the solution.
Grades have been assigned according to the following scores (incl. bonus points):
A: > 42
B: 38 - 42
C: 32 - 37
D: 28 - 31
E: 24 - 27
Fx: 22 - 23
F: < 22
For those of you who have received Fx, please contact Pierre. Your task for obtaining a passing grade will involve the topics on which you performed poorly on the exam (different for different individuals). Note that scores close to a passing grade have been re-checked after the initial grading. Thus, for any complaints on such scores you should make sure that you can make a strong case for why you should be awarded more points.
From the statistics (see next section) it is clear that problems 4 and 5 were more difficult than expected. In particular, the most common mistakes on both problems concerned basic probability, such as computing expectations and covariances, rules for conditioning and similar.
The other somewhat unexpected outcome was the poor performance on problem 3b. This was mainly due to many of you not formulating your intuitive thoughts on the problem in proper mathematical terms. Most of you, especially students who passed the exam, seemed to have an idea of how the solution should go, but did not / were not able to formulate it in a precise manner.
Statistics
Total number of students that took the exam:
## [1] 54Number of students that passed:
## [1] 31Histogram for individual final scores (including bonus points): 
A box plot for the score on the five problems: 
Summary statistics for all students:
## Prob 1 Prob 2 Prob 3 Prob 4
## Min. : 0.000 Min. : 0.000 Min. : 0.000 Min. : 0.000
## 1st Qu.: 5.250 1st Qu.: 3.000 1st Qu.: 0.000 1st Qu.: 0.000
## Median : 9.000 Median : 5.500 Median : 4.000 Median : 2.000
## Mean : 7.444 Mean : 5.593 Mean : 3.519 Mean : 2.333
## 3rd Qu.:10.000 3rd Qu.: 8.750 3rd Qu.: 6.000 3rd Qu.: 3.750
## Max. :10.000 Max. :10.000 Max. :10.000 Max. :10.000
## Prob 5 Bonus Exam Sum
## Min. : 0.000 Min. :0.000 Min. : 0.00 Min. : 2.00
## 1st Qu.: 0.000 1st Qu.:1.000 1st Qu.:17.00 1st Qu.:20.25
## Median : 4.000 Median :2.500 Median :22.50 Median :26.00
## Mean : 4.481 Mean :2.778 Mean :23.37 Mean :26.15
## 3rd Qu.:10.000 3rd Qu.:5.000 3rd Qu.:30.00 3rd Qu.:31.75
## Max. :10.000 Max. :5.000 Max. :50.00 Max. :55.00Summary statistics for students who passed the exam:
## Prob 1 Prob 2 Prob 3 Prob 4
## Min. : 2.000 Min. : 1.000 Min. : 0.000 Min. : 0.000
## 1st Qu.: 8.500 1st Qu.: 5.000 1st Qu.: 2.500 1st Qu.: 0.000
## Median :10.000 Median : 7.000 Median : 5.000 Median : 3.000
## Mean : 8.903 Mean : 6.935 Mean : 4.806 Mean : 3.419
## 3rd Qu.:10.000 3rd Qu.:10.000 3rd Qu.: 7.000 3rd Qu.: 5.500
## Max. :10.000 Max. :10.000 Max. :10.000 Max. :10.000
## Prob 5 Bonus Exam Sum
## Min. : 0.000 Min. :0.000 Min. :20.00 Min. :24.00
## 1st Qu.: 3.000 1st Qu.:2.000 1st Qu.:25.00 1st Qu.:29.00
## Median : 8.000 Median :4.000 Median :30.00 Median :30.00
## Mean : 6.355 Mean :3.355 Mean :30.42 Mean :33.77
## 3rd Qu.:10.000 3rd Qu.:5.000 3rd Qu.:33.00 3rd Qu.:37.50
## Max. :10.000 Max. :5.000 Max. :50.00 Max. :55.00Summary statistics for students who failed the exam:
## Prob 1 Prob 2 Prob 3 Prob 4
## Min. : 0.000 Min. : 0.000 Min. :0.000 Min. :0.0000
## 1st Qu.: 2.000 1st Qu.: 1.000 1st Qu.:0.000 1st Qu.:0.0000
## Median : 6.000 Median : 3.000 Median :1.000 Median :0.0000
## Mean : 5.478 Mean : 3.783 Mean :1.783 Mean :0.8696
## 3rd Qu.: 8.000 3rd Qu.: 5.000 3rd Qu.:4.000 3rd Qu.:2.0000
## Max. :10.000 Max. :10.000 Max. :5.000 Max. :4.0000
## Prob 5 Bonus Exam Sum
## Min. : 0.000 Min. :0 Min. : 0.00 Min. : 2.00
## 1st Qu.: 0.000 1st Qu.:0 1st Qu.: 9.00 1st Qu.: 9.50
## Median : 0.000 Median :2 Median :16.00 Median :18.00
## Mean : 1.957 Mean :2 Mean :13.87 Mean :15.87
## 3rd Qu.: 3.000 3rd Qu.:4 3rd Qu.:19.00 3rd Qu.:21.50
## Max. :10.000 Max. :5 Max. :23.00 Max. :23.50The grade distribution was as follows:
## A: 9.259259 %## B: 5.555556 %## C: 25.92593 %## D: 20.37037 %## E: 11.11111 %## Fx: 11.11111 %## F: 31.48148 %