October 2016
Beginner to intermediate
328 pages
6h 58m
Chinese
Content preview from Data Science from Scratch中文版｜用Python學資料科學
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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.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.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.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.
69
第六章
機率
機率理論一般來說都是對的，但在某些情況下卻很荒謬。
——愛德華 · 吉朋（Edward Gibbon）
如果對
機率
和相關數學沒有一定程度的瞭解，恐怕很難做好資料科學的工作。不過本
章的做法和第 5 章很類似，我們只會做些簡要的介紹，而不會深入太多的細節。
我們的目的，就是希望能讓你理解機率的概念，它指的是從某個事件
空間
（
universe
of
events）中挑選出某個
事件
（
event
），衡量其中不確定性的一種量化方式。如果想要搞
懂前面這種充滿術語的說法，還不如直接來個例子：各位可以想想丟骰子的情況。所
謂的事件空間，其中包含了所有可能的結果。若從其中取出部分結果，就可以形成一
個事件；舉例來說，「骰子丟出 1 點」和「骰子丟出偶數」都可算是一個事件。
我們會用
P
(
E
) 這樣的寫法，來表示「事件
E
的機率」。
我們可以用機率理論來建立模型，也可以用機率理論來評估模型。事實上，我們到處
都會不斷用到機率理論。
如果你有興趣的話，可以進一步深入理解機率的哲學與
內涵
（如果還能來瓶啤酒，那
就更棒了！）。不過，我們在這裡並不會做太深入的說明。
相依與獨立
大體上來說，如果我們知道「事件
E
是否發生」可以協助我們判斷「事件
F
是否發
生」（或是反過來的情況），我們就會說
E
和
F
這兩個事件是「
相依的
」（
dependent
）。
要不然的話，我們就會說這兩個事件是「
獨立的
」（
independent
）。
舉例來說，假設我們丟兩次銅板，即使知道「第一次丟出正面」，我們還是無法知道
「第二次丟出正面」的情況會不會發生。這
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
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.