Lesson Sources of Errors in Sampling

Objectives Understand how error can be introduced during sampling

Vocabulary Nonsampling errors – errors that result from the survey process. Can be due to nonresponse of individuals selected, inaccurate responses, poorly worded questions, etc Bias – nonsampling error introduced by giving preference to selecting some individuals over others, by giving preference to some answers by wording the questions a particular way, etc Sampling errors – error that results from using sampling to estimate information regarding a population. Occurs because a sample gives incomplete information about the population

Sources of Nonsampling Error Incomplete Frame Nonresponse Data Collection errors –Interviewer error –Misrepresented answers –Data-entry (input) errors Questionnaire Design –Poorly worded questions –Inflammatory words –Question order –Response order

Sampling ErrorNon sampling Error Iceberg Sampling Process Analysis Process Interviewer errors Collection Execution Data-entry (input) errors Designer Incomplete Frame Questionnaire Design Poorly worded questions Inflammatory words Question order Response order Subject Nonresponse Misrepresented answers sample gives incomplete information about the population Errors in Sampling

Four basic sampling techniques Simple random sampling (SRS) Stratified sampling –Some of all Cluster sampling –All of some Systematic sampling

Summary and Homework Summary –Stratified and cluster sampling are different –Convenience sampling results are generally suspect Homework –pg 37-39: (all), 24, 25