Accepted for/Published in: JMIR Human Factors
Date Submitted: Jul 16, 2025
Date Accepted: Jan 19, 2026
Mode effects between telephone and web interview in the post-COVID-19 questionnaire survey CoVerlauf: exploratory study
ABSTRACT
Background:
Concurrent mixed-mode designs for data collection may introduce mode-specific biases. This study examined sample characteristics and questionnaire response patterns of participants selecting Computer-Assisted Website Interviewing (CAWI) and Computer-Assisted Telephone Interviewing (CATI) in the CoVerlauf study (Germany, 2021).
Objective:
The first objective was to identify associations between participants’ choice of the interview mode (CAWI vs. CATI), their characteristics and the number of reported post-COVID-19 symptoms. The second objective was to identify the influence of the mode choice on response patterns to multiple-choice and free-text items about post-Covid-19 symptoms.
Methods:
Data from 1779 CoVerlauf participants were analyzed. A logistic regression assessed how mode-choice related to participant characteristics and experienced post-Covid-19 symptoms. Two mixed-effects logistic regressions examined associations between mode-choice and response to free-text items. We also assessed whether mode-specific effects influenced overall results of the CoVerlauf study.
Results:
Among participants, 77.8% (1384/1779) chose CAWI and 22.2% (395/1779) CATI. Odds of selecting CATI were lower for higher education participants (OR 0.46, 95% CI = 0.34 – 0.63), those represented by another person (OR 0.28, 95% CI = 0.13 – 0.56), and each additional symptom experienced at the time of interview collected from multiple-choice items (OR 0.86, 95% CI 0.77 – 0.96). Compared to 50-59, the odds increased with age (60-69 years: OR 2.26, 95% CI 1.53 – 3.36;70-79: OR 4.98, 95% CI 3.12 – 7.97; 80 or older: OR 17.29, 95% CI 9.34 – 33.11) and each additional symptom experienced at infection collected from multiple-choice (OR 1.09, 95% CI 1.04 – 1.15) and free-text items (OR 1.94, 95% CI 1.61 – 2.37). Odds of responding free-text items were higher among CATI participants (OR 5.22, CI 95% 4.25 – 6.42), females (OR 1.57, CI 95% 1.30 – 1.89), those with at least three pre-existing conditions (OR 1.44, CI 95% 1.07 – 1.96), missing ISCED information (OR 1.95, CI 95% 1.11 – 3.42), and for each additional multiple-choice symptom (OR 1.15, CI 95% 1.12 – 1.19). Odds of collecting additional symptoms from free-text answers were lower for CATI participants (OR 0.58, 95% CI: 0.41 – 0.82), but increased for each additional multiple-choice symptom (OR 1.08, 95% 1.02 – 1.14), two or more pre-existing conditions (2: OR 1.8, CI 1.02 – 3.00; 3+: OR 2.0 CI: 1.18 – 3.43), and ages 40 to 49 (OR 2.0, 95% CI 1.13 – 3.55).
Conclusions:
While mode choice influenced response patterns, especially to free-text items, it did not affect the overall findings of the CoVerlauf study.
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