Consent to send survey questions by SMS

All IP13 respondents who said they use a mobile phone were asked for consent to be sent occasional survey questions via SMS. The location of this consent was experimental manipulated, being either early on in the survey (in the Demographics module) or at the end of the survey (in the Contact Details module). The controlling variable allocating respondents equally to the two conditions was generated within the questionnaire, with equal allocation occurring at the respondent level. The variable controlling this experiment is smsconsent on record m_indresp_ip:

1          Consent asked in Demographics module

2          Consent asked in Contact Details module

The variables affected by this experiment are on the record m_indresp_ip: consentsms_early, consentsms_late.

At Wave 15, questions about SMS consent were asked again, but were not manipulated experimentally. Updates were made to the previous procedure by: repeating the consent for SMS questions for everyone who did not consent in IP13;  the consent question was only asked in the Contact Details module; one follow-up question was added about reasons for not consenting; and a subset of questions from the IP12/IP13 Mobile Device Use module were repeated to understand respondents’ mobile use.