October 2021
Intermediate to advanced
289 pages
8h 31m
Chinese
Content preview from 数据科学中的实用统计学(第2版)
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42
｜
第
2
章
抽取其他样本，则仍然会存在样本偏差。
自选择抽样偏差
在
Y
elp
这样的社交媒体上，关于餐厅、旅店和咖啡馆之类的评论很容易有
偏差，因为提交评论的人员并不是随机选择的；相反，他们都有撰写评论的
动机。这就会导致自选择偏差。想撰写评论的人可能有糟糕的体验，也可能
与这些商家有某种关联，或者可能只是与那些没有撰写评论的人不同的一类
人。请注意，虽然自选择样本可能无法可靠地表示事物的真实状态，但在相
似商家之间的简单比较中，自选择样本的可靠性会增加，因为同样的自选择
偏差会发生在每个商家身上。
2.1.1
偏差
统计学中的偏差指的是在测量或抽样过程中产生的系统性测量误差或抽样误差。需要重点
区分的一点是，误差是由随机性造成的，还是由偏差造成的。看一下用枪打靶这个实际过
程，射击不会每次都正中靶心，甚至可能脱靶。无偏过程会产生误差，但误差是随机的，
并不会明显地偏向某个方向（见图
2-2
）。
图
2-3
中的结果展示了一个有偏过程——
x
轴方
向和
y
轴方向仍然存在随机误差，而且还存在偏差，因为射击点更多地落在了第一象限。
图 2-2：准星正常的枪的射击散点图
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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.