Statistics
REGRESSION
By the end of data collection, data on both respondents and non-respondents, intervention and control groups etc. was stored inhouse and prepared for analysis. The response proportion was calculated as the number of respondents divided by the number of invited individuals before the delivery of the first postal reminder (day 22 from initial invitation) to prevent interference from postal respondents who have or may not have seen the digital invitation. Further, the final response proportion was calculated for all respondents by the end of the survey. Descriptive statistics and univariate logistic regression modelling of the 186,133 study participants were conducted to answer the research questions. In all analyses, the dependent variable indicates whether the sample member has (fully or partially) completed the questionnaire. In the first step, the independent variable was a dichotomous indicator of intervention (animation vs. no animation). This analysis will give an initial indication of whether, on average, the letters with animation videos have any overall effect on response propensity (Table 