Computer Science 280: Homework 11

Posted: 4/14/04

Due: 4/21/04


Section
Number
Point
Comments
6.5
4
3


6
4


18
4


20
4


34
4
Write this up carefully

47
3

adhoc
A
4
Show that the variance of the Poisson distribution with parameter lambda is also lambda. You'll find it helpful to compute E(X^2) by writing k^2=k(k-1) +k.

B
3
Show that for any real number "a", Var(aX)=a^2*Var(X).

C
3
Compute the mean and the variance of the normalized binomials that were used in the CLT example (slide #1 in "probability6.pdf").

D
6
You are trying to estimate the probability "p" that a coin lands "H". How large should n be so that your empirical average (#of H in n flips / n) is within 0.01 to "p" with probability of at least 0.9? You will found the following useful: Chebyshev's inequality, the maximum of p*(1-p) is <= 1/4.

E
2
From past experience a professor knows that the test score of a student taking the final exam is a random variable with mean 75. Give an upper bound for the probability that a student's test score will exceed 85.

F
2
Suppose that in addition the professor knows the variance of a student's test score is equal to 25. What can be said about the probability that a student will score between 65 and 85?