If you want to survey one and the same respondent over different periods of time, you are usually dealing with a multi-wave survey, a longitudinal study or a diary study which all three face two challenges:
SoSci Survey is offering a number of functions to ensure and facilitate the implementation of multi-wave surveys.
Technically, there a two possibilities to implement a multi-wave survey with SoSci Survey. Both do have their advantages and disadvantages and for both the following recommendation applies: you should test them carefully prior to your study - for example with shortened field time (a time interval of 5 minutes instead of 7 days) and temporary email addresses.
The first option is to create one questionnaire under Create a Questionnaire.
This contains the pages for the first wave, an interruption page and, subsequently, the pages for the second wave.
At first, the interruption page shows a Thank-You-note (for the first part of the questionnaire). If the respondent is returning to that page - after a previously defined time interval (for example through mailResume() or via a question type that sends an email to personal contacts) - the interruption page redirects the participant automatically to the next page which starts the second questionnaire. Programming an interruption page is documented and explained under the reference for the command mailResume().
value() or replace() - for example, for filter questions or for adjusting questions to respondents' answers through placeholders.option('progress',…) or has to be deactivated completely, because it would count over both parts of the questionnaire otherwise.In diary studies usually the same questions are presented in every survey wave - and moreover the data are supposed to be analysed with multilevel analyses. A solution with multiple questionnaires is suggested if…
When using multiple questionnaires for every completed questionnaire a new dataset (data row) is stored. For matching reasons every data row needs a distinct participant code. By doing the following one can get such a code:
Compared to one questionnaire which is completed step by step (see above), the option of single distinct questionnaires has the following advantages and disadvantages:
Depending on the design of the study, participants might all receive an invitation to the second survey wave at the same point in time or the moment is depending on when they completed to first questionnaire (also, a random assignment of intervals is possible, see MESM below).
Sending an invitation at a previously defined point of time can be obtained directly via the user interface:
In case the invitation to the second part is dependend on when recipients participated in the first part, a little PHP-code will be necessary (see also Introduction to PHP). Using the function mailSchedule() it is possible to determine at which point of time an invitation will be sent to certain groups of participants.
In an ideal situation the participant will be invited to the first part of the questionnaire already by mailings. If an email address is is previously unknown the proceedings are described in the chapter Multi-Wave Surveys with Self-Recruited Respondents.
In the first questionnaire, preferably at the end, on a page that dropouts usually do not reach, the command mailSchedule() is positioned, for example:
mailSchedule(false, 2, 7 * 24 * 3600);
The first parameter „false“ says that an invitation shall be sent to a participant who just completed the questionnaire. The second paramter „2“ determines that the invitation with the number 2 shall be sent. The third parameter schedules the invitation to be sent in exactly 7 days, indicated in seconds (an hour has 3600 seconds, following this „7*24*3600“ gives you the number of seconds for 7 days). Important: Every invitation via mailings can only be sent once to every participant. If you want to send one and the same email several times, you have to copy this mail. The corresponding PHP-code might look as following (here for 5 days every day an invitation will be sent):
mailSchedule(false, 2, strtotime('+1 day'));
mailSchedule(false, 3, strtotime('+2 day'));
mailSchedule(false, 4, strtotime('+3 day'));
mailSchedule(false, 5, strtotime('+4 day'));
mailSchedule(false, 6, strtotime('+5 day'));
In the example above the function strtotime() was applied.
It creates an Unix-timestamp (number of seconds since 1.1.1970) out of a string-input. „+1 day“ will be become „tomorrow at the same time“. „+1 day 8:00“ would become „tomorrow at 8 o'clock in the morning“.
When working with previously determined intervals (for sending an invitation), it is easy to create a reminder mail as a new mailing and send it.
When working with relative intervals, you will have to prepare the invitation to the second part of the questionnaire as well as the reminder mail during the first questionnaire using the command mailSchedule(). Consequently, without any further ado, both mailings will be sent:
mailSchedule(false, 2, strtotime('+7 day')); Invitation the the second questionnaire
mailSchedule(false, 3, strtotime('+8 day')); Reminder mail one day later
In a second step, you will have to ensure that the reminder will not be sent if the participant completes the second questionnaire.
In order to do so, you will have to position the command mailRevoke(). This function will delete the planned sending from the schedule.
mailRevoke(false, 3);
Multi-wave studies allow for multi-variant designs. The following paragraph is dedicated to specific cases of application:
For multi-wave studies it is of advantage that email addresses of participants are known. With these you can send them personalized invitations to the second, third,… part of the questionnaire. In case the email addresses are previously unknown, the following chapter describes some solutions: Multi-Wave Surveys with Self-Recruited Respondents.
In a diary study one usually creates three questionnaires:
If email addresses are unknown you might need a fourth questionnaire for registration of the participants (Multi-Wave Surveys with Self-Recruited Respondents).
A mailing is created for every email or reminder that a participant shall receive. For example, two mailings for the previous questionnaire (invitation and reminder) and one per day. In the list of mailings is a button which easily and fast creates copies of mailings (button: duplicate).
Subsequently, for every email with „Preparing Sending“ it will be determined at which point of time it will be send.
Tip: To which addresses an email will be send, will identified right at time of sending - in case it is a standardized interval for all addresses. Consequently, addresses can be added even after determining the time and date of sending.
Important: Please choose the questionnaire to which a mail shall refer to only in the tab „link to questionnaire“, if you are using placeholders like %link% and %link.html% in the invitation. The placeholder ensures that data rows will contain personal identifications in the variable SERIAL.
Mobile Experience Sampling is a special type of diary studies. Thereby participants receive at random intervals (within a certain timeframe) SMS messages on their smartphone. Those messages ask the participants to complete a preferably short questionnaire.
The counterpart to experience sampling is that respondents call up a questionnaire independently when a specific event occurs. Ideally, they do not have to enter a personal code each time, but can use a personalized link directly. There are several ways to do this:
Search terms: panel, panel studies, experience sampling, ambulatory assessment.