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  • 24 votes cast
Jun
15
comment What is the probability that a boy who knows how to solve $25$ of potential $30$ questions will get at least $8$ of $10$ correct?
See stats.stackexchange.com/q/22285
Jun
15
awarded  Critic
Jun
15
comment Michael Spivak's Calculus - Chapter 1 Problem 6
In case (iii), an odd exponent will preserve the signs of $x$ and $y$, so $y^n$ must remain greater than $x^n$.
Jun
15
answered Writing the pdf for a Gamma Distribution
Jun
12
comment Bijective function between lists and sets
You can generalize this to a bijection between an $n$-length binary string with $1$ appearing $k$ times and a $k$-element subset $S$ of the set of integers between $1$ and $n$. The bijection (mapping subsets to binary strings) would look like $f(S)=a_{1}a_{2}...a_{n}$, where $a_{i}=\begin{Bmatrix} 0 & i\notin S\\ 1 & i\in S \end{Bmatrix}$. You should be able to see that the number of $n$-bit strings where $1$ appears exactly $k$ times is the same as the number of ways to select a $k$-element subset from $\left [ n \right ]$.
Jun
5
answered Combination of trees
Jun
4
comment Primal and dual problem (Optimal solution) - Operations research
Perhaps this answer to a related question will help.
Jun
4
comment Primal and dual problem (Optimal solution) - Operations research
Have you learned about complementary slackness yet?
Jun
4
awarded  Yearling
Jun
3
awarded  Commentator
Jun
3
answered Work Problem that deals with Number of Men, Days, Leaving
Jun
3
comment What is the most rigorous proof of the irrationality of the square root of 3?
Some answers can be found at math.stackexchange.com/q/64643 and math.stackexchange.com/q/131391 and math.stackexchange.com/q/930486.
Jun
2
comment Help with a Taylor expansion
This Wikipedia article may be of use. You'd drop the $\frac{2}{\sqrt{\pi }}$, though.
Jun
2
awarded  Teacher
Jun
2
comment Probability of Opening a Combination Lock
@NotALoner you begin entering all codes whose sum is 8 That sounds like OP is trying to say you remember previous tries.
Jun
25
awarded  Editor
Jun
25
revised What is the intuition behind $P(X={\lambda})\ {\equiv}\ P(X={\lambda}-1)$ for a Poisson distribution
added condition that lambda minus 1 be a nonnegative integer
Jun
25
comment What is the intuition behind $P(X={\lambda})\ {\equiv}\ P(X={\lambda}-1)$ for a Poisson distribution
@nrpeterson Thank you. I'll explicitly add the condition that lambda is a nonnegative integer.
Jun
25
awarded  Student
Jun
25
asked What is the intuition behind $P(X={\lambda})\ {\equiv}\ P(X={\lambda}-1)$ for a Poisson distribution