Go to the menu "Respondents" and "Respondents". Here you can view the statistics for the total of the respondents and per type of respondent. There are four types of respondents:
Unsubscribers: have unsubscribed from the study or entire account.
Did not participate: have not yet participated in the study (no question answered yet).
Incompletes: out: have started the Survey, have answered at least 1 question but have not completed it.
Completes: have completed the Survey.