Bias Source	Bias	Description	In This Paper
Sampling bias	Sample composition	Differences in sample selection are due to the use of different survey sampling frames for RDD and ABS samples [@114213]. Differences in coverage (i.e., coverage bias) can arise from different modes potentially attracting different kinds of respondents to take the survey [@114223].	Section 3.1.1
	Respondent non-response	Potential differences in respondent non-response between modes have to do with potential differences in the number and type of invited sampled persons who chose not to participate in the survey [@114201].	Section 3.1.2
Measurement bias	Mode measurement unequivalence	Differences due to respondents answering a question differently because of the way the question is presented [@114208 chap. 23]; the differences may also be situational and/or motivational [@114206].	Section 3.2
	Straightlining or satisficing	The tendency of providing satisfactory but not optimal answers to reduce effort [@114212]. Straightlining, a kind of satisficing, is responding with identical ratings to a series of questions [@114232].	Section 3.3
	Acquiescence bias	The tendency of the respondent to favor the ‘yes’ or ‘agree with’ answer regardless of the content of the question [@114203].	Section 3.4
	Social desirability bias	The bias caused by participants under-reporting socially undesirable behaviors and/or over-reporting socially desirable behaviors to comply with social norms, is a major source of response bias in survey research [@114198; @114211].	Section 3.4