The document contains 10 questions about probability concepts such as expected value and variance. Question 1 asks the student to calculate and summarize in a table the probability of finding a lost flash drive on the 1st, 2nd, etc. drive picked from a drawer containing 10 identical drives. Question 2 involves calculating the expected distance and variance that someone will walk to find a lost flash drive randomly dropped along a 5km circular track. Question 3-4 involve calculating expected values and variances for game moves determined by dice rolls and random number generation. The remaining questions cover topics such as probability of roots for random quadratic equations, normal distributions, random number generation experiments, and card games.
Must show work for each question. When doing this homework, you ma.docx
1. Must show work for each question.
When doing this homework, you may find the following
identities useful: (see attached photo)
Question 1.
Albert has saved his homework in a flash drive and put the drive
in a drawer, without realizing that there are already 9 drives in
that drawer. Now, there are 10 drives, and they all look
identical.
If he now picks up the drives randomly one by one and checks
whether it contains his homework, what is the probability that
the
k
th drive that he picks up contains his homework, for
k
= 1
,
2
,
3
, . . . ,
10? Summarize your result in a table to show the probability
distribution.
Let
X
be the number of drives that he picks up until he finds his
homework. Find the expected value
E
2. (
X
)
.
Find the variance
V
(
X
)
.
Question 2.
Every day Albert jogs on a circular track that is 5-kilometer
long. Yesterday, he dropped a flash drive somewhere on the
track. He is going back today to look for the drive.
If he picks a random location on the track to start, and then
walks in a clockwise direction until he finds the drive, what is
the probability that the he will find the drive after walking for
no more than
x
kilometer?
Let
X
be the distance, measured in km, that he will have walked when
he finds the drive. Find the expected value
E
(
X
)
3. .
Find the variance
V
(
X
)
.
Question 3.
Becky is playing a board game. She throws two fair, 6-faced
dice with the numbers 1–6 on them, and the sum will determine
how many spaces she will move.
Let
X
be the number of spaces that she will move. Find the expected
value
E
(
X
)
.
Find the variance
V
(
X
)
.
Question 4.
4. Becky is playing a board game in which she glides along a path
continuously instead of jumping from one space to another. She
uses a random number generator to get two numbers from the
continuous uniform distribution on [1,6], and the sum will
determine how far she will move.
Let
X
be the distance that she will move. Find the expected value
E
(
X
)
.
Find the variance
V
(
X
)
.
Hint: The uniform distribution is on [1,6], not [0,6]. Think
about the implications.
Question 5.
5. If we pick a number
k
randomly from the uniform distribution on [0
,
1]
,
what is the probability that the equation
x
2
+ 5
kx
+ 1 = 0 has 2 distinct real roots?
Questions 6–10 are on the next page.
Question 6.
If we pick a number
k
randomly from the normal distribution with
µ
= 1
, σ
= 2; what is the probability that the equation
x
2
+
kx
+ 1 = 0 has 2 distinct real roots?
Question 7.
6. large group of people are raising money for charity. The
amounts of money that they have raised are normally
distributed, with mean being $100 and standard deviation being
$30. If we select one person at random, and consider the amount
of money raised by this person;
what is the probability that this amount exceeds $110?
what is the probability that this amount is less than $105?
what is the probability that this amount is between $85 and
$100?
Question 8.
Write a program to generate random numbers in the following
manner:
Generate a random number
x
from the continuous uniform distribution on [0,1).
√
•
Calculate
y
=
7. x.
Use
y
as the output.
Conduct a numerical experiment to see how the random numbers
are distributed. Use the same setup as in Homework 1: provide
extensive comments to the source code, submit the source code,
conduct 10 experiments, with 10
6
trials in each experiment, and tabulate the results. To show the
results:
If you are comfortable using numpy, matplotlib, etc, to make
histograms; please do that.
If not, here is a quick-and-dirty way to see what the distribution
may be:
Divide the interval [0,1) into
n
sub-intervals, for some large
n.
(For our purpose, choosing
n
= 10 or larger would be okay.)
Count how many random numbers there are in each sub-interval.
Scale to obtain the percentages.
Tabulate or plot the percentages.
Comment on the results. What is the probability distribution of
y
? Justify you claim algebraically.
Question 9.
8. There are 10 cards with the numbers 1, 2, 3, 4, 5, 6, 7, 8, 9, and
10 on them. If we randomly draw a card, with each card being
equally likely to be drawn, what are the expected value and the
variance?
Question 10.
In a standard deck of playing cards, there are 4 suits, and in
each suit, there are 13 cards: A, 2, 3, 4, 5, 6, 7, 8, 9, 10, J, Q,
and K.
Suppose we count A as 1; and J, Q, and K as 10; and all the
other cards at the numbers being shown. If we randomly draw
cards from such a deck, with each card being equally likely to
be drawn, what are the expected value and the variance?
Suppose we count A as 11; and J, Q, and K as 10; and all the
other cards at the numbers being shown. If we randomly draw
cards from such a deck, with each card being equally likely to
be drawn, what are the expected value and the variance?