问题如下：
Based on the table below, which of the following statements is correct?
Frequency Distributions of Sample Returns
选项：
A.The relative frequency of Interval C is 15.
The cumulative frequency of Interval D is 100%.
The cumulative relative frequency of Interval C is 92.3%.
解释：
C is correct because the cumulative relative frequency of an interval tells us the fraction of all observations that are less than the upper limit of an interval. For Interval C, that would be (2 + 7 + 15)/26 = 92.3%.
A is incorrect because the relative frequency of an interval is the absolute frequency of that interval divided by the total number of observations, here 15/26 = 57.7%. The number 15 represents Interval C’s absolute frequency (also known as frequency), which is simply the actual number of observations in a given interval.
B is incorrect because the cumulative frequency tells us the number of observations that are less than the upper limit of a return interval, not the percentage of observations meeting that criteria. Because Interval D is the uppermost return interval, its cumulative frequency is the total number of observations for all intervals, yielding 2 + 7 + 15 + 2 = 26 and not 100%, which is the cumulative relative frequency for Interval D.
可是讲义的32页那张表里最后一列的Cumulative Frequency 就是百分比形式， Culmulative Absolute Frequency 才是 累计加数。题目问的是Cumulative Frequency啊？
