Statistical analysis
REGRESSION
Statistical analyses were performed using STATA software version 16.0 (STATA LP, College Station, TX). The database was locked to this questionnaire survey on October 6, 2021. A comparison between the questionnaire participants and questionnaire non-responders was performed using the student’s t-test and chi-squared test. Answers to the questions related to screening preference were converted to a binary: “I will receive” and “others” (including “I will not receive” and “Unknown”). For binary data, frequency, percentage, and 95% confidence intervals were calculated. To compare knowledge about HPV before and after participating in this trial, McNemer’s test was conducted. McNemer’s test was also performed to compare the willingness to undergo two hypothetical screenings—screening with a doctor-collected sample and that with a self-collected sample. As a sensitivity analysis, the willingness was compared excluding participants who selected “I had an opportunity to undergo cytology testing other than the screening provided by the city” as the reason for not undergoing screening. As post-determined analyses, experience of self-sampling, knowledge about HPV, and willingness to undergo screening were compared with age and duration without screening using the chi-squared test and logistic regression analysis. After calculating the estimates using logistic regression analysis, a linear trend test was performed using the “contrast p.” command of STATA. For this analysis, items of self-sampling experience were converted into a binary: “Agree” (including “Fully agree” and “Somewhat agree”) and “Others” (including “Neither agree nor disagree,” “Somewhat disagree,” and “Fully disagree”). Missing values were included in the aggregate but excluded from the statistical test. A two-tailed p-value of <0.05 was considered significant.