Probit offers mail mode, self-administered survey options to our clients.  While not often used for large-scale general public surveys, many clients chose to mix mail with online when collecting a full-coverage sample.  For the traditional mail mode survey, the questionnaire is mailed to the offline portion of a random sample. A typical mail-mode survey package consists of the outgoing envelope, cover letter, questionnaire, return envelope, and possibly an incentive.  Reminder post cards are often employed, and a mix-mode design, designed to mirror reminder email invitations.  The respondents complete and return the questionnaires. Probit offers full data entry service with this methodology.