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Results tagged with probability
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user 771714
For questions about probability. independence, total probability and conditional probability. For questions about the theoretical footing of probability use [tag:probability-theory]. For questions about specific probability distributions, use [tag:probability-distributions].
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1
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74
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Conditional probabilities: Transmitting bits.
The probability of a transmission error is 1%. Furthermore, we know that $P(S_1)=p$ and thus $P(S_0)=1-p$. … I know the formulas and I decoded the probability of a transmission error as follows:$$P((S_0\cap E_1)\cup (S_1\cap E_0))$$ I also figured that $P(E_0|S_0)+P(E_1|S_0)=P(E_0|S_1)+P(E_1|S_1)=1$, but I can't …
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answer
21
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Arbitrarily many stationary distributions of a markov chain
Consider the following Markov chain on $\{-1, 0, 1\}$. In each step of
the Markov chain we flip a coin $Y \in\{0, 1\}$ and a coin $Z\in \{+1,
> -1\}$ and set $X_{n+1} = X_n +Y\cdot Z\cdot \mathbf{1}_ …
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34
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Prove that $\frac{1}{n}S_n\to -1$ a. s. and $\frac{1}{n}E[S_n]\to 0$
frac{1}{n}S_n\to -1$ almost surely as $n\to \infty$
Attempt
Using Borel-Cantelli, we have $\sum \limits_{n=1}^{\infty}P(X_n=n^{2})=\sum \limits_{n=1}^{\infty}\frac{1}{n^2}<\infty$, which implies the probability … That means $X_n=-1$ for sufficient $n$ with probability $1$. This implies that $$S_n=\frac 1 n \sum\limits_{k=1}^{n} X_k \to -1$$ almost surely. …
1
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1
answer
56
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Combinatorics: Distributing tasks in class
Suppose you sit in a class room with $n$ students. There are $k$ question and every student can pick $5$ of them. How many different ways are there such that no question is left out?
In total we have …
2
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2
answers
67
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A bartender and a customer roll a six-sided, ungalvanized cube. What is his chance of winning?
A bartender and a customer roll a six-sided, ungalvanized cube. If the
visitor throws a higher number than the bartender, he wins. A guest is
a rascal who cheats. He takes advantage of the waiter's i …
3
votes
2
answers
108
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Is $\mathcal{A}\vee \mathcal{B}=\{A\cup B : A\in \mathcal{A}, B\in \mathcal{B}\}$ a $\sigma$...
Let $\mathcal{A}$ and $\mathcal{B}$ be $\sigma$ algebras over $\Omega$. I know that $\mathcal{A}\cup \mathcal{B}$ is not a $\sigma$-algebra, but what about $\mathcal{A}\vee \mathcal{B}=\{A\cup B : A\i …
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1
answer
24
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What is the maximum value that $P[D]$ can take?
Let $A$, $B$, $C$ be three events with $P[A] = 0.7$, $P[B] = 0.7$ and $P[C] = 0.7$. Let $D$ be the event "exactly one of the three events $A$, $B$, $C$ occurs". What is the maximum value that $P[D]$ c …
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2
answers
112
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If you throw a dice $10$ times, what is the probability that there is at least one $1$ and a...
If you throw a dice $10$ times, what is the probability that there is
at least one $1$ and at least one 6? …
2
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1
answer
44
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A càdlàg function $f: [0,T]\to \mathbb{R}$ has only a finite amount of jumps bigger than $1/n$.
Statement
Let $n\in \mathbb{N}$. A càdlàg function $f: [0,T]\to \mathbb{R}$ has only a finite amount of jumps $\Delta f_t=f_t-f_{t-}$ with $|\Delta f_t|\geq 1/n$
Proof (Reductio ad absurdum)
Suppose, …
2
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1
answer
53
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Finding $E(XY)$ where $X$ and $Y$ are dependent.
$X$ and $Y$ are defined on $\Omega=\{1,2,3,4\}$ (we have a discrete uniform distribution) where $$X(\omega)=\begin{cases}1, \text{ if } \omega \text{ even} \\ 0, \text{ else}\end{cases} \text{ and }Y( …
2
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1
answer
65
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On the Borel-Cantelli lemma - Is this argumentation valid?
I read that as saying "The probability that the event $\{X_n=n^2\}$ will happen infinitely many times is $0$". …
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answers
22
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Using the De Moivre–Laplace theorem (Voters)
How likely
is it if the coin toss is instead in favor of Proposal $B$ with
probability $p=0.505$. …
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1
answer
41
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Conditional expectation of geometrically distributed random variable
Given $Y$ as a geometrically distributed random variable with $p\in (0,1)$, what is $E[Y|Y\geq 10]?$
I got:$$E(Y|Y\geq 10)=\frac{E(\mathbf{1}_{Y\geq 10}Y)}{P(Y\geq 10)}=\frac{E(\mathbf{1}_{Y\geq 10}Y) …
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1
answer
51
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Why is $E(f(X,Y)|\mathcal{F}_t)=\int f(x,Y)P^{X|\mathcal{F}_t}(dx)$?
Given a filtered probability space $(\Omega, \mathcal{F}, (\mathcal{F}_t)_t, P)$ and with notation (regular conditional probabiltiy assumed): $$P^{X|\mathcal{F}_t}(B)=P(X\in B|\mathcal{F}_t)=E(1_B(X)|\ …
2
votes
1
answer
19
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Finding a transformed random variable's distribution
Let $Y\sim \operatorname{Geo}(p)$ with $P(Y=k)=p(1-p)^k$. Furthermore, $\hat{Y}\sim \operatorname{NegBin}(2,p)$, i. e. $P(\hat{Y}=k)=kp^2(1-p)^{k-1}$.
I want to find $P(\lfloor U\widehat{Y} \rfloor=k) …