Suggested Answers to Odd-Numbered Questions
[A Guide to Econometrics, 5th edition, 2003, by Peter Kennedy]
A1(a) This Monte Carlo study examines the sampling distribution of the average of 25
numbers drawn from a distribution with mean 2 and variance 9.The average of N
numbers drawn randomly from a distribution with mean and variance 2 has a
sampling distribution with mean and variance 2/N.
(b) Abar estimates the mean of this sampling distribution, so should be close to 2.
(c) Avar estimates its variance, so should be close to 9/25 = 0.36.
A3(a) This Monte Carlo study examines the sampling distribution of the fraction of
successes h in a sample of size 50 where the probability of success is 20%. When the true
probability of success is p, for a sample of size N then h has a sampling distribution with
mean p and variance p(1-p)/N.
(b) hav should be an estimate of 0.2.
(c) hvar should be an estimate of p(1-p)/N which here is ( 0.2)(0.8)/50 = 0.0032
(d) wav estimates the mean of the sampling distribution of the estimated variance of h,
and so should be approximately 0.0032.
A5. Create 44 observations from a normal distribution with mean 6 and variance 4.
Calculate their average A and their median B. Repeat to obtain , say, 1,000 As and 1,000
Bs. Find the mean of the 1,000 A values and the mean of the 1,000 B values and see
which is closer to 6. Calculate the variance of the 1,000 A values and the variance of the
1,000 B values and see which is smaller.
A7. i) Choose values for a and b, say 2 and 6 (be sure not to have zero fall between a and
b because then an infinite value of 1/x2 would be possible and its distribution would not
have a mean). ii) Get the computer to generate 25 drawings (x values) from U(2, 6). (If
the computer can only draw from U(0,1), then multiply each of these values by 4 and add
2.) iii) Use the data to calculate A's estimate A* and B's estimate B*. Save them. iv)
Repeat from ii) 499 times, say, to get 500 A*s and 500 B*s. v) Obtain the mean m of the
Category | exam bundles |
Comments | 0 |
Rating | |
Sales | 0 |