Which of the following is appropriate for displaying data collected on the different brands of cars students at a major university drive? ( )
A. Pareto chart
B. B. two-way classification table
C. histogram
D. D. scatter plot
一个样本容量n=5的数据集为:7、4、9、8、2,中位数为______
假设数据近似服从正态分布,均值为30,标准差为5,则根据切比雪夫定理可知,落在15~45范围内的数据占总数据的百分比至少为______
若离散型随机变量x服从二项分布,且n = 10,p = 0.70,则x的期望E(x)=______ ;方差Var(x)=______