OG里的可能错误？

drealityUID: 2223599

OG里的一个例子：
Example 4.2.6: In the list of 16 numbers 2, 4, 4, 5, 7, 7, 7, 7, 7, 7, 8, 8, 9, 9, 9, 9, the range is 9−2=7, the first quartile is Q1 =6, and the third quartile is Q3 =8.5. So the interquartile range for the numbers in this list is 8.5 − 6 = 2.5.

我算出来的：Q1=6.5, Q3=8.25
和OG里的不一样，感觉自己算的应该没错呀...

Orion_ChangUID: 3582304

你再感觉下。。。  或者去看看ETS对 first quartile，third quartile，interquartile range的定义


注意有多套conventions，而ETS作为标准的那一套可能和你以前学习的不一样。

drealityUID: 2223599

Orion_Chang 发表于 2017-10-13 18:40
你再感觉下。。。  或者去看看ETS对 first quartile，third quartile，interquartile range的定义

额...跳着看OG的，发现前面说了他们的算法，和我的不一样...
那碰到的话按ETS的来？感觉OG里的算法好奇怪...

drealityUID: 2223599

好吧，找到ETS的说明了。但似乎没考虑到数量是奇数的情况？例如：2，4，4，4，5
此时ETS的方法先找出M=4, 再划分两个等同数量的组，但是此时没法划分为两个等同数量的组了呀？

Because the number of data in a list may not be divisible by 4, there are various rules to determine the exact values of Q1 and Q3 and some statisticians use different rules, but in all cases Q2 = M. We use perhaps the most common rule, in which Q2 = M divides the data into two equal parts — the lesser numbers and the greater numbers—and then Q1 is the median of the lesser numbers and Q3 is the median of the greater numbers