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in SoSci Survey (English) by s089524 (140 points)
closed by SoSci Survey

Hello, I have set a serial mail function in a first survey (collect participant's email without participant needing to confirm email address), so that participants could receive an automatic invitation for a follow-up survey 4 weeks after the first one. I have tested this and everything seemed to be working fine.

I am however now on week 2 of my data collection and after data inspection, I see that some participants were already invited for follow-up. This seems to happen in two cases:

  • When participants don't finish their participation on day 1, they receive an immediate invitation for the Follow-up --> I guess this is something I could have added in the code of my serial mail, but it's not problematic since participants' data need anyway to be excluded since there's no data for day 1
  • One single other participant finished the survey on day 1, and seems to have received the invitation for the follow-up immediately or on the next day (participant did first survey on the 20th February at night and follow-up on the 21st in the morning.

I have till now ca. 100 participants and this problem seems till now to only have happened by one of the last participants. I am however afraid that there is some problem with the serial email function and we will get more participants whose participation in the follow-up is invalidated since the 4 week interval is not fulfilled.

Would there be any suggestions on why this might be and how can I make sure it doesn't happen to the next participants?

Furthermore, is there anyway how I can send this one participant a new follow-up link in 4 weeks (I don't have access to the e-mail addresses correspondence to the participant code).

Thank you in advance!

closed with the note: No more information received on the issue.
by s089524 (140 points)
Update: I have tried it myself as a participant, and unfortunately I also received a link for the follow up just a few hours later.

The PHP code that I'm using, and that had been working till now is:
mailSchedule(value('VPID01'), 1, strtotime('+28 days'));
mailSchedule(value('VPID01'), 2, strtotime('+29 days'),

1 is the first invitation for the follow up 4 weeks later and the 2 is a reminder.
by SoSci Survey (308k points)
Seems correct on first glance. Any other PHP code that might cause the mail being sent? And other questionnaires in the survey project? What does the debug information say? https://www.soscisurvey.de/help/doku.php/en:create:debugging
by s089524 (140 points)
The debug information seems consistent (no error, it shows the planned date of sending correctly).
We are using two questionnaires: day 1 and Follow-up. The only PHP code we have is this one on day 1: Page 3 has the OptInEmail, PHP is on top of Page 4 followed by 4 "Text Input" questions, Page 5 continues then with multiple questions but no PHP anymore.
The follow-up questionnaire has no PHP and can only be assessed by the link provided in the invitation mail.

Thank you for your help!
by SoSci Survey (308k points)
> The debug information seems consistent (no error, it shows the planned date of sending correctly).

Then I would assume that the mailing is scheduled twice ... correctly one time, and too early another time. Note, that the mail will only be sent the first time.

However, I cannot explain where the second entry would come from. Would you like to post a pretest/debug URL, so I could register an email address and track the issue in the database?
by SoSci Survey (308k points)
Thanks, I just added a test case. The debug information says:

(21.03.2024, 15:24) and
(22.03.2024, 15:24)

The database confirms that, using the unix timestamps 1711031068 and 1711117468.

I will now wait for an email to arrive early... do I have to do the whole questionnaire in order to trigger anything?
by SoSci Survey (308k points)
20 Minutes now, an no email so far. Could it be that your email address that received an early mail had already been in your address list from an earlier test, let's say, 1 monath ago?
by s089524 (140 points)
Yes! Indeed I had already the email address in the list from an earlier test! Could that be what happened also to the participant, that they gave their email address twice (probably didn't finish first participation)? I tried it again with an email address that was not on the list and I didn't receive any invitation for the follow-up till now.

If that's the case, could it be that a second invitation, after the 4 weeks, is still sent again to those participants?
by SoSci Survey (308k points)
> If that's the case, could it be that a second invitation, after the 4 weeks, is still sent again to those participants?

Depends on what you set in the opt-in question. If the question allows for duplicates, another address entry was created that will receive its emails independently. But, if you did not change the default option to avoid duplicates, the email will not be sent to the email address twice.

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