Use the Momentary type if you want participants to be alerted by their mobile device when it's time to take the survey.
When you select "Momentary" from the drop down menu an additional pop-up window will open up. This allows you to set the times of day within which the alerts will occur. By default the Start and End times are set to 8:00 AM and 6:00 PM Monday - Friday. You can choose to leave these as they are or change the times or days as you wish. No alerts will be sent outside the times set in this window (i.e. times in white section). At least one day must be completed.
The times are determined by the time on the mobile device on which the App is operating so you do not need to adjust the times to accommodate those in other time zones.
Finally, decide how frequently you want alerts to be sent by choosing either Minute(s) or Hour(s) and entering a number into the Interval box. Then choose to check the Randomization box or not. For example, if you entered "Every 120 minutes" without checking the Randomization box then your participant will be alerted every 120 minutes beginning at 8:00AM (or whatever Start Time you have entered) until the end time (6PM), that is, at 8:00, 10:00, 12:00, 14:00 and 16:00.
If you do check the Randomization box then the alert will be sent at some randomly determined point within the first 120 minutes (e.g. between 8.00am and 10.00am) and every subsequent 120 minute block until the End Time. To prevent overlapping survey windows where two instances of the same survey are available simultaneously, the mEMA system will automatically create a 10% time buffer between time intervals. If you choose an interval of 120 minutes and the Daily Data Collection period begins at 8:00am then no surveys will be scheduled for the first and last 10% of this interval. 10% of 120 minutes is 12 minutes, thus, no surveys will be scheduled between 9:48am (i.e. 12 minutes before the end of the first interval) and 10:12am (12 minutes after the start of the second interval).
You will see the schedule now in the table at the end of the scheduling box. It shows you when each alert is scheduled for and when the window will open and close. Press Create schedule from parameters and you will see the assignment appear in the table on the My Surveys page. If you click the Edit you can return to the Survey Assignment box to make changes.