【简答题】Liam works in Sydney. Last week he had 41 holiday, but he didn’t know 42 to go. He said to his friend Robert, “I 43 the hot weather here, but I can’t find a cool place in Australia. How will I spend m...
【简答题】In his last will, he listed his wife and children as the ____________. (benefit)
【单选题】Child mortality (死亡率)decreased due to improvements in medical care and greater attention to problems related to proper________.
【单选题】设随机变量X与Y的相关系数为0.9,若Z=X-0.4,则Z与Y的相关系数为
【简答题】简述随机抽样与非随机抽样的含义及各自具体包含哪些抽样方法。
【简答题】设随机变量X和Y的相关系数为0.9,若Z=X-0.4,则Y与Z的相关系数为________.
【单选题】He is not easy-going, but his trust in his friends will last forever once _______.
【单选题】将总体中的全部个体区分为容量及结构相似的不同的子总体,以子总体为单位按照简单随机抽样的方法抽取一定数量的子总体,再将这些被抽中的子总体中所包含的个体合并起来形成最终的样本,这种抽样方法称作