September 2013
Intermediate to advanced
264 pages
5h
Chinese
Content preview from Bad Data 技術手冊
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第二章：是只有我這樣，還是這個資料本身令人感到有趣？
依據精準的定義，如 CTR 這種數值的比例不應該超過 1。當然，不論定義為何，它仍然
有可能會超過 1（畢竟本書是在講壞資料 ...），但它通常都不應該超過 1。特別是你發現
值是幾百或幾千時，那就很有可能有問題了。
財務值應該也有合理的上限。至少在我所處理過的資料種類中，PPC 與 CPC 的值在數
百美元左右應該是合理的，絕對不會是數千美元以上。你的可允許範圍很有可能會不
同，但不論範圍為何，請確保讓資料看起來是合理的。
你也能夠查看欄位的平均值（或是類似如模數或是中位數等的統計方式），來看看它是
否合理。舉例來說，若某個小東西的售價是大約 10 元美金，但在你的「小東西售價」
欄位中的平均是 999 元美金，那麼一定就是發生某些錯誤了。這也能夠幫助確認單位。
若這個欄位是用「角」為單位，而不是用「元」當單位，那麼 999 就是一個合理的值。
這種確認的好處就是它們可以很容易的被自動化，這對會定時更新的資料集合來說是非
常有用的。花幾個小時來確認新的資料集合並不會太麻煩，並且可能可以獲得對於該資
料的直覺想法，但若要一直重複執行就不是那麼有趣了。並且，若你擁有一個每小時更
新的 rss 摘要，你可能要像迪士尼樂園中 Jungle Cruise 的導遊一樣地工作（「我覺得超
有趣，我想要再玩一次！再一次！再一次！」）。
視覺化
另一個我發現非常有用的技巧就是，在一個資料欄位中建立值的統計直方圖。這對於非
常大型的資料集合特別有幫助，因為前面所討論的單純統計僅能知道資料的表面。統計 ...
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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.
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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.