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b:head_first_statistics:poisson_distribution [2025/10/07 06:53] – [Exercise] hkimscilb:head_first_statistics:poisson_distribution [2025/10/07 08:42] (current) – [Poisson Distribution] hkimscil
Line 46: Line 46:
 \end{eqnarray*} \end{eqnarray*}
  
 +<code>
 +> dpois(3, 2)
 +[1] 0.180447
 +>
 +
 +</code>
 ====== What does the Poisson distribution look like? ====== ====== What does the Poisson distribution look like? ======
  
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 \end{eqnarray*} \end{eqnarray*}
  
-r을 이용한다면 ''pbinom'' 을 이용한다.+r을 이용한다면 ''pbinom'' 혹은 ''dbinom'' 을 이용한다.
  
 <code> <code>
 > pbinom(q=2, 10, 0.3) > pbinom(q=2, 10, 0.3)
 [1] 0.3827828 [1] 0.3827828
-> </code>+ 
 +> sum(dbinom(0:2, 10, 0.3)) 
 +[1] 0.3827828 
 +>  
 + 
 +</code>
  
 손으로 계산을 한다고 하면,  손으로 계산을 한다고 하면, 
Line 389: Line 400:
  
 \begin{eqnarray*} \begin{eqnarray*}
-P(X = 0) & = & {10 \choose 0} * 0.3^0 * 0.7^10 \\+P(X = 0) & = & {10 \choose 0} * 0.3^0 * 0.7^{10\\
 & = & 1 * 1 * 0.028 \\ & = & 1 * 1 * 0.028 \\
 & = & 0.028  & = & 0.028 
Line 420: Line 431:
 \begin{eqnarray*} \begin{eqnarray*}
 P(X=0) & = & \frac {e^{-1}{1^0}}{0!} \\ P(X=0) & = & \frac {e^{-1}{1^0}}{0!} \\
-& = & \frac {e^-1 * 1}{1} \\+& = & \frac {e^{-1* 1}{1} \\
 & = & .368  & = & .368 
 \end{eqnarray*} \end{eqnarray*}
 </WRAP> </WRAP>
 +
 +<code>
 +> dpois(0, 1)
 +[1] 0.3678794
 +
 +> ppois(0, 1)
 +[1] 0.3678794
 +
 +</code>
  
 <WRAP box> <WRAP box>
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 & = & 0.488 & = & 0.488
 \end{eqnarray*} \end{eqnarray*}
 +
 +<code>
 +> sum(dgeom(0:2,0.2))
 +[1] 0.488
 +>   
 +> pgeom(2, 0.2)
 +[1] 0.488
 +
 +
 +</code>
 +
  
 기대값과 분산은 각각 $1/p$, $q/p^2$ 이므로 $5$와 $20$. 기대값과 분산은 각각 $1/p$, $q/p^2$ 이므로 $5$와 $20$.
 </WRAP>  </WRAP> 
  
b/head_first_statistics/poisson_distribution.1759787592.txt.gz · Last modified: by hkimscil

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