Postcode Checks
All randomized participants’ postcodes were checked (enrollments had now risen to n=915) to assess whether they matched with the first line of an address provided by Royal Mail Postcode Finder [Different options were considered to avoid future bot responses, including Qualtrics’ fraud detection software options, such as a reporting tool to indicate whether a response is likely to be a bot [A second round of checks on participants (n=196) were reviewed to identify whether any bots had enrolled (1) since the original checks but before the addition of the CAPTCHA and (2) following its addition. A further 181 suspicious entries were identified as enrolling (in the intervening period between the original checks and the addition of the CAPTCHA).