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标题: 请教关于standard deviation的一道题 [打印本页]

作者: 兰漂漂 时间: 2008-3-9 03:05 标题: 请教关于standard deviation的一道题

During an experiment, some water was removed from each of 6 water tanks. If the standard deviation of the volumes of water in the tanks at the beginning of the experiment was 10 gallons, what was the standard deviation of the volumes of water in the tanks at the end of the experiment?

(1) For each tank, 30 percent of the volume of water that was in the tank at the beginning of the experiment was removed during the experiment.

(2) The average (arithmetic mean) volume of water in the tanks at the end of the experiment was 63 gallons.

Answer：A

为何我做出来的是选C 呢？请TX指教！

作者: Freehorser 时间: 2008-3-15 10:47

帮你顶一下

一碰上这类题目我就犯晕

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