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1st SEMESTER 2021/22 FINAL EXAMINATION

BACHELOR DEGREE Year 4

MTH305

RISK MANAGEMENT


Problem Solving Excel Work (100 marks)

Please attempt all the following problems using the given Excel template on the learning mall.

Q1

Suppose we back-test a VaR model using 800 days of data. If the VaR model used is accurate, the probability of the VaR being exceeded on any given day is p. We can consider two alternative hypotheses:

H0 : The probability of an exception on any given day is p.

H1 : The probability of an exception on any given day is greater than p.

From the properties of the binomial distribution, the probability of the VaR level being exceeded on m and more days is

k(n)=m k!( pk (1 − p)nk

The VaR confidence level is 99% and we observe 10 exceptions.

1) Calculate the expected number of exceptions. [2 marks]

2) Using the BINOMDISTfunction in Excel, calculate the probability of 10 or more exceptions. [5 marks]

3) At a 5% significant level, should we accept or reject the VaR model? [3 marks]

10 marks

Q2

Table 1 Annual Default Ratesfor All Rated Companies, 1975-1996

Year

Default Rate

Year

Default Rate

1975

0.00361

1986

0.0183

1976

0.00176

1987

0.01423

1977

0.00354

1988

0.01393

1978

0.00354

1989

0.02226

1979

0.00088

1990

0.03572

1980

0.00344

1991

0.02803

1981

0.00162

1992

0.01337

1982

0.0104

1993

0.00899

1983

0.0095

1994

0.00651

1984

0.00869

1995

0.00899

1985

0.00952

1996

0.00506

SOURCE: Moodys.

18 marks

Table 1 shows the default ratesfor all rated companies in the US between 1975

and 1996. If a company defaults, its loans will default as well. Based on the one- factor Gaussian copulafor a portfolio of loans, wefind that the probability

densityfunctionfor default rate is

g(DR) = exp { [(N−1(DR))2