Tagged Questions
0
votes
1answer
374 views
Probability 2 people have a birthday in the same month out of 7
What is the probability that 2 people in the group have a birthday in the same month out of 7 people?
I know the answers 88.85% however I want to know how to work it out using factorials instead of ...
1
vote
1answer
66 views
Probability and Counting
I have just picked up a text on discrete math and its been ages since I have done this so if anyone can show me with steps to correct my fault, that would be so great.
Repair facility has 25 failed ...
1
vote
1answer
72 views
Word and Latex: Probability
I was practicing my probability and counting solving ability when I came across this rather interesting question on the web:
The Reviews editor for a certain scientific journal decides ...
1
vote
1answer
54 views
Dice probability problem collection
I tag these questions as homework, as they are older exam questions and every year
Can you try to solve/explain how to solve with a method some of these?
If something is answered in an old post ...
1
vote
2answers
45 views
Ballot boxes probability problem collection
I tag these questions as homework, as they are older exam questions and every year
Can you try to solve/explain how to solve with a method some of these?
If something is answered in an old post ...
2
votes
0answers
74 views
Longest consecutive subsequence bound with limit
Let $S\subseteq \{1,2,\ldots,n\}$ and let $X(S)$ be the length of maximal consecutive subsequence in $S$.
For example: if $S=\{4,5,7,8,9,11,12\}$ then $X(S)=3$ because of the subsequence $\{7,8,9\}$.
...
4
votes
1answer
85 views
An intuitive solution to this problem (Using probability tree)
A group of boys has been lost several days in the dessert. This group has a phone to make phone calls. After a long way walk, they believe that the current area is suitable for phone calls; even ...
2
votes
2answers
186 views
Expected value and Variance of a Random Variable
I understand Mean (Expected Value) and Variance of Random variables as outlined on this page. I can't seem to apply those concepts to this problem, however.
Say there's a class of 50 people answering ...
3
votes
2answers
128 views
Probability of rolling at least one 6 while rerolling 1's
Scenario: You roll a number of 6-sided dice
Success: Roll at least one 6
Conditions: You can re-roll any 1's you get on the first roll
What are the odds of success for n dice?
Example: 7 dice
...
0
votes
2answers
31 views
Variance of n Bernoulli Trials
Count the variance of n Bernoulli trials with each probability of success is p.
Let random variable $X_i$ be
$1$ if trial is success, or
$0$ if trial fails.
Then expected value $E(X_i) = 1 ...
1
vote
0answers
45 views
Proving a variable as discrete random (confusing question)
A box contains 3 white and 3 black marbles. In a game, 3 marbles are randomly selected from the box. The score (X) is equivalent to the getting of 10 white marbles. Show that X is a discrete random ...
7
votes
2answers
235 views
Given three integers in $\{0,\ldots,100\}$ which sum up to $100$. What is the probabilty that two of them are the same?
We pick $3$ numbers (one by one) from set $\{0,1,...,100\}$.
What is probabilty that two numbers are the same if sum of those $3$ numbers is $100$?
My solution:
Which two are the same we can pick in ...
3
votes
1answer
40 views
Regarding calculating the bias of coin with uncertainty
Suppose you have a coin that you flip $n$ times and the result have $m$ heads and $n-m$ tails. How accurate can you predict the bias of the coin to be $\frac m n$?
I know that ...
1
vote
1answer
57 views
Regarding probability bound of flip coins
Suppose you flip a fair coin 10,000 time how can you characterize the distribution of the occurrence of head?
From the textbook, it says that $P[head>\frac{n}2 + k\sqrt{n}]$ < $e^{-{k^2/2}}$, ...
0
votes
1answer
25 views
Expected value of index of the minimum element in an array
I'm stuck the following assignment:
What is the expected value of the index of the minimum element in an array of n distinct integer that are randomly ordered?
I think it should be something like:
...
