单项选择题
The number of class intervals in a frequency distribution is usually between （）.
A.3 and 5 B.7 and 9 C.5 and 15 D.1 and 25
单项选择题 A cumulative frequency polygon is also called （）.
单项选择题 If the individual class frequency is divided by the total frequency, the result is the （）.
单项选择题 If data are grouped into intervals and the number of items in each group is listed, this could be called a （）
