NO.PZ2020010304000036
问题如下：
For the following data:
a. What is the median?
b. What is the IQR?
选项：
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).
做题思路都是默认第一个数的概率是0%，然后其余的数平分100%的概率，并按照从小到大和累计概率来排序，是这样吗？
假如这道题是11个数，那么升序排列后概率依次为0%、10%······100%，
（假如还是这些数）四分之一分位点就是：q25%=0.27*50%+0.28*50%=0.275；
或者用线性差值法来做：（x-0.27）/（0.28-0.27）=（25%-20%）/（30%-20%）
辛苦老师解答！
