August 2015
Intermediate to advanced
272 pages
5h 46m
Japanese
Content preview from Think Stats 第2版 ―プログラマのための統計入門
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77
6
章
確率密度関数
†
6.1
PDF
CDF
の導関数は確率密度関数（
probability density function
、
PDF
）と呼ばれます。
例えば、指数分布の
PDF
は次のようになります。
PDF
expo
(x)
＝
λ
e
−
λ
x
正規分布の
PDF
は次のようになります。
PDF
normal
(x)
＝
1
σ
√
2
π
exp
[
−
1
−
2
(
x
−μ
σ
)
2
]
ある値
x
について
PDF
を計算することはあまり意味がありません。結果は確率で
はなく確率密度だからです。
物理学では、密度は単位体積当たりの質量と定義されます。質量を計算するために
は、体積を乗じるか、密度が一定でないなら全体にわたって積分する必要があります。
似たように、確率密度（
probability density
）は
x
の単位当たりの確率を表します。
確率質量を計算するためには、
x
について積分しなければなりません。
thinkstats2
は確率密度関数を表すクラス
Pdf
を提供します。
Pdf
オブジェクトは、
次のようなメソッドを提供します。
†
本章のコードは、
density.py
にある。コードのダウンロードや扱い方については、
viii
ページの「コード
を使う」を参照してほしい。
78
6 章 確率密度関数
Density
値
x
を取り
x
での分布の密度を返します。
Render
離散集合の値に対して確率密 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.