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math121b:04-15 [2020/04/14 22:52]
pzhou [How to play the probability game?]
math121b:04-15 [2020/04/15 09:44] (current)
pzhou
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 ** Conditional Probability **: suppose we want to know "given that $A$ happens, what is the probability $B$ will happen?"  ** Conditional Probability **: suppose we want to know "given that $A$ happens, what is the probability $B$ will happen?" 
-$$ \P(A | B) := \frac{ \P(A \cap B) } {\P(B) \} $$+$$ \P(A | B) := \frac{ \P(A \cap B) } {\P(B) } $$
  
 ** The product rule ** ** The product rule **
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 ===== How to play the probability game? ===== ===== How to play the probability game? =====
 First thing first, find out what is $\Omega$ and $\P$.  First thing first, find out what is $\Omega$ and $\P$. 
 +
 +Be aware when someone say: "let me randomly choose ...." 
  
 Here is an interesting example: [[https://en.wikipedia.org/wiki/Bertrand_paradox_(probability) | Bertrand Paradox ]] Here is an interesting example: [[https://en.wikipedia.org/wiki/Bertrand_paradox_(probability) | Bertrand Paradox ]]
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 +Another hard example: let $M$ be a random symmetric matrix of size $N \times N$, where each entry is iid Gausian. Question: how does eigenvalues of this matrix distribute? 
  
  
  
  
math121b/04-15.1586929921.txt.gz · Last modified: 2020/04/14 22:52 by pzhou