[求助]做PREP时碰到的一道有关统计的数学题

adele07smile · 发表于 2006-4-23 17:44:00

7.51 8.22 7.86 8.36
8.09 7.83 8.30 8.01
7.73 8.25 7.96 8.53
A vending machine is designed to despense 8 ounces of coffee into a cup.After a test that recorded the number of ounces of coffee in each of 1,000 cups dispensed by the vending machine, the 12 listed amounts, in ounces, were selected from the data. If the 1,000 recorded amounts have a mean of 8.1 ounces and a standard standard deviation of 0.3 ounce, how many of the 12 listed amounts are within 1.5 standard deviations of the mean?
答案是11
完全没明白这题是什么意思，如何做
请NN指点

adele07smile · 发表于 2006-4-23 18:02:00

望路过的NN指点

谢谢！

salvador · 发表于 2006-4-23 18:10:00

mean＝8.1

standard deviation ＝0.3

within 1.5 standard deviations of the mean=[8.1-0.3*1.5,8.1+0.3*1.5]=[7.65,8.55]

all the numbers except 7.51 fall within such interval

so answer is 11

adele07smile · 发表于 2006-4-23 18:16:00

0.3*1.5是什么意思啊

salvador · 发表于 2006-4-23 18:28:00

以下是引用adele07smile在2006-4-23 18:16:00的发言：

0.3*1.5是什么意思啊

how many of the 12 listed amounts are within 1.5 standard deviations of the mean?

adele07smile · 发表于 2006-4-23 18:55:00

明白了

我把最后一句的意思理解错了

我还以为1.5也是标准方差

事实上standard deviations of the mean是宾语

within 1.5 是状语

呵呵笨啊

谢谢

salvador · 发表于 2006-4-23 19:49:00

[求助]做PREP时碰到的一道有关统计的数学题

[求助]做PREP时碰到的一道有关统计的数学题

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