为什么是除以60？

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%.