A.必须相同
B.必须不同
C.可以相同，也可以不同
D.完全没有关系
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A.population
B.sample
C.parameter
D.statistic
A.midpoint frequency
B.cumulative frequency
C.stem and leaf plot
D.relative frequency
A.提高
B.下降
C.不变
D.条件不够，无法判断
A.全距
B.标准差
C.平均差
D.标准差系数
A.1.2
B.0.8
C.1.25
D.0.83
A.the number of classes must be less than 10
B.each data point can only fall into one class
C.the width of each class is equal to the range
D.the number of intervals must be an odd number
A.One form of descriptive statistics uses graphical techniques
B.One form of descriptive statistics uses numerical techniques
C.In the language of statistics，the term population refers to a group of people
D.Statistical inference is used to draw conclusions or inferences about characteristics of populations based on sample data
The number of phone calls arriving at a switchboard each hour has been recorded and the following frequency distribution has been developed.
What is the cumulative frequency of the third class？（）
A.80
B.0.40
C.155
D.75
A.it contains more class intervals
B.the values of the original data are retained
C.the class midpoints are used as the stem
D.the class midpoints are used as the leaf
A.是等距分组
B.第一组假定下限是0
C.相邻组限是重叠的
D.分组标志为连续型变量
E.某学生的成绩80分应归在70-80这一组
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