diff --git a/luku24.tex b/luku24.tex index 03e04b1..a4bd1aa 100644 --- a/luku24.tex +++ b/luku24.tex @@ -85,7 +85,7 @@ corresponds to the set Each outcome $x$ is assigned a probability $p(x)$. Furthermore, the probability $P(A)$ of an event -that corresponds to a set $A$ can be calcuted as a sum +that corresponds to a set $A$ can be calculated as a sum of probabilities of outcomes using the formula \[P(A) = \sum_{x \in A} p(x).\] For example, when throwing a dice, @@ -135,7 +135,7 @@ Here $5/6$ is the probability that the outcome of a single throw is not six, and $(5/6)^{10}$ is the probability that none of the ten throws is a six. -The complement of this is the answer for the problem. +The complement of this is the answer to the problem. \subsubsection{Union} @@ -164,7 +164,7 @@ the probability of the event $A \cup B$ is simply The \key{conditional probability} \[P(A | B) = \frac{P(A \cap B)}{P(B)}\] -is the probability $A$ +is the probability of $A$ assuming that $B$ happens. In this situation, when calculating the probability of $A$, we only consider the outcomes @@ -172,7 +172,7 @@ that also belong to $B$. Using the above sets, \[P(A | B)= 1/3,\] -Because the outcomes of $B$ are +because the outcomes of $B$ are $\{1,2,3\}$, and one of them is even. This is the probability of an even result if we know that the result is between $1 \ldots 3$. @@ -318,7 +318,7 @@ The expected value for $X$ in a uniform distribution is \index{binomial distribution} ~\\ In a \key{binomial distribution}, $n$ attempts -are done +are made and the probability that a single attempt succeeds is $p$. The random variable $X$ counts the number of @@ -413,7 +413,7 @@ The next distribution is $[0,1,0,0,0]$, because we can only move from floor 1 to floor 2. After this, we can either move one floor up or one floor down, so the next distribution is -$[1/2,0,1/2,0,0]$, etc. +$[1/2,0,1/2,0,0]$, and so on. An efficient way to simulate the walk in a Markov chain is to use dynamic programming. @@ -510,7 +510,7 @@ the array in increasing order. It is easy to calculate any order statistic in $O(n \log n)$ time by sorting the array, but is it really needed to sort the entire array -to just find one element? +just to find one element? It turns out that we can find order statistics using a randomized algorithm without sorting the array. @@ -675,7 +675,7 @@ both colors is $1/2$. In a random coloring, the probability that the endpoints of a single edge have different colors is $1/2$. Hence, the expected number of edges whose endpoints -have different colors is $1/2 \cdot m = m/2$. +have different colors is $m/2$. Since it is excepted that a random coloring is valid, we will quickly find a valid coloring in practice.