Modeffekt

Modeffekt, or mode effect, is a term used in survey methodology to describe systematic differences in survey results that arise from the mode of data collection rather than from actual differences in the population being studied. Different modes such as face-to-face interviews, telephone interviews, mail surveys, and online questionnaires can lead respondents to answer differently, even when the underlying attitudes or behaviors are the same.

Causes of modeffekt include social desirability bias in interviewer-administered modes, perceived anonymity in self-administered modes, differences in question presentation and visual layout, varying degrees of respondent engagement, and slightly different opportunities to skip questions. The strength and direction of the effect can vary by topic, population, and mode combination, making cross-mode comparisons challenging.

Modeffect is typically assessed through experimental designs that compare responses obtained via different modes or through statistical adjustments that attempt to calibrate responses across modes. Researchers monitor differences in prevalence estimates, means, and response distributions to quantify the impact of the mode.

Implications of modeffekt are significant for survey comparability and trend analysis. When surveys use different data collection methods over time or across studies, observed changes may reflect mode effects rather than real changes in the population.

Mitigation strategies include careful survey design to minimize mode-driven differences, mixed-mode or sequential design with mode-switching experiments, mode-specific weighting, and calibration studies that align measurements across modes. Transparent reporting of the data collection mode and any adjustments is also recommended.