[单选题]Sampling error is defined as:A.An error that occurs when a sample of less t
[名词解释] 便利取样(convenience sampling)
[名词解释] CD(cluster of differentiation)
[名词解释] 分层抽样(stratified sampling)
[名词解释] 系统抽样(systematic sampling)
[名词解释] 丛集性头痛(cluster headache)
[名词解释] 简单随机取样(simple random sampling)
[单选题]There is/are_________consonant cluster(s)in the word“infrastructure”.A.0B.1
[名词解释] 聚类分化群(cluster of differentiation,CD)