_______ refers to a situation in which some unit selected for a sample refuses to participate. CensusNon-response Unit errorBias

The term you are looking for is Non-response. It refers to a situation in which some units selected for a sample refuse to participate in a survey or study. This can lead to bias if the non-respondents have significantly different characteristics or opinions compared to those who do respond. When non-response occurs, it can impact the accuracy and validity of the results obtained from the sample, making it important for researchers to consider ways to address or minimize non-response in their sampling strategies. Understanding non-response is crucial for ensuring that survey findings are representative of the larger population and can influence decisions made based on that data.