cumulative relative frequency是啥

问题如下：

An investment fund has the return frequency distribution shown in the following exhibit：

Which of the following statements is correct?

选项：

A.The relative frequency of the bin "-1.0 to +2.0" is 20%

B.The relative frequency of the bin "+2.0 to +5.0" is 23%

C.The cumulative relative frequency of the bin "+5.0 to +8.0" is 91.7%.

解释：

A is correct. The relative frequency is the absolute frequency of each bin divided by the total number of observations. Here, the relative frequency is calculated as: (12/60) x 100 = 20%. B is incorrect because the relative frequency of this bin is (23/60) x 100 = 38.33%. C is incorrect because the cumulative relative frequency of the last bin must equal 100%.