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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38
3 章 確率質量関数
いまのところ、この結論はとりあえずのものです。同じデータセットを用いて目に
見える相違は何かを明らかにし、その相違が明らかになる可視化を選びました。この
効果が実際のものかどうかは確かではありません。ランダムな偶然による変動かもし
れません。この問題については後で触れます。
3.4
クラスサイズのパラドックス
次に行く前に、
Pmf
オブジェクトでどんな計算ができるかの一例を示したいと思
います。この例を私は「クラスサイズのパラドックス」と呼んでいます。
アメリカの多くの大学では、学生と教授の人数比は約
10:1
です。しかし、実際に
授業に出席したら、クラスの平均人数が
10
人より多いことに気付くでしょう。この
食い違いには
2
つの理由があります。
•
学生は通常
1
学期当たり
4
〜
5
クラス取るものですが、教授はせいぜい
1
、
2
クラスしか授業を行わない。
•
受講者が少ない授業に参加する学生は少なく、受講者の多い授業を取る学生
の数は（当たり前ですが）多い。
1
番目の影響は（少なくとも気付いてしまえば）明白ですが、
2
番目の影響はすぐ
にはわからないかもしれません。そこで、次のような例を考えてみましょう。ある大
学ではある学期に
65
のクラスを開講しています。それぞれの学生数が次のようになっ
たとします。
学生数
クラス数
5-9 8
10-14 8
15-19 14
20-24 4
25-29 6
30-34 12
35-39 8
40-44 3
45-49 2
39
39
3.4 クラスサイズのパラドックス
もし学部長に平均クラス人数を尋ねたら、 ...
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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.