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小王爱学习 · 2022年01月12日

没看懂第二问答案

NO.PZ2020010304000036

问题如下:

For the following data:

a. What is the median?

b. What is the IQR?

解释:

a. The first step is to rank order the observations.

From here, we anchor the first observation at 0% and the last at 100%, equally spacing the in-between val-ues. The divisions here will be 100/n-1 = 20%:

The median (50%) lies exactly half way between the third and fourth ranked observations. Therefore:

Median=(0.28+0.38)/2=0.33

b. This requires calculating the 25% and 75% levels.

The 25% level is 5/20 = 25% of the way between ranked observations 2 and 3. Therefore: q25% = 0.75 * 0.27 + 0.25 * 0.28 = 0.2725

Similarly, the 75% level is 75% of the way between observations 4 and 5: q75% = 0.25 * 0.38 + 0.75 * 0.43 = 0.4175

Thus, IQR = (0.2725, 0.4175).

100/4 等于25。那么应该6/4 F分成四份。然后第一个和第二个的平均数是25%。
2 个答案

DD仔_品职助教 · 2022年01月13日

嗨,爱思考的PZer你好:


75%的数据也是同理,根据rank我们可以判断在4和5这两个数据之间,利用线性插值法:(75%-60%)/(x-0.38)=(80%-60%)/(0.43-0.38)

得 x=0.4175

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加油吧,让我们一起遇见更好的自己!

DD仔_品职助教 · 2022年01月13日

嗨,爱思考的PZer你好:


同学你好,具体的分位点要看最后一列rank的信息来确定,不是简单的分割,你这样想不准确。

我们现在是有6个数,但是第一个数的rank是0%,第二个数rank是20%,第三个数是40%,那么可以确定25%是在第二个数和第三个数之间的,那么我们现在假设这个25%的数字是x,利用线性差值法来进行计算:(25%-20%)/ (x-0.27) = (40%-20%)/(0.28-0.27) 可得,x=0.2725



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虽然现在很辛苦,但努力过的感觉真的很好,加油!

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