本节概要(1) To understand the concept of sampling To learn the steps in developing a sampling pla an To understand the differences between probability samples and nonprobability samples To understand the concepts of sampling error and nonsampling error本节概要（1） • To understand the concept of sampling. • To learn the steps in developing a sampling plan. • To understand the differences between probability samples and nonprobability samples. • To understand the concepts of sampling error and nonsampling error