F.5 standard deviation(1)

2010-12-26 8:42 am

(1) For a set of data which are not entirely the same, the mean is 7. If a datum '7' is removed from the set of data, what will be the change in the standard deviation?

(2) For a set of data which are not entirely the same, the mean and maximum value are 8 and 15 respectively. If a datum '15' is added to the set of data, what will be the change in the standard deviation?

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回答 (1)

用戶9112

2010-12-26 7:33 pm

✔ 最佳答案

http://img17.imageshack.us/img17/9939/90764299.png

圖片參考：http://img17.imageshack.us/img17/9939/90764299.png

2010-12-26 20:17:41 補充：
(1) 睇錯題目:
Mean is not change. Therefore sum of (x_i - x_bar)^2 is not changed.
But sample size n is reduced =>standard deviation will increase.

2010-12-26 20:17:46 補充：
(2) After careful calculation, the change in standard deviation cannot be deterimined. It depends on the original standard deviation and the data size.
Please see the calculation here:
http://img831.imageshack.us/img831/899/24746729.png

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