Survey response rate
Not all survey projects send out reminders simply because they are concerned about harassing customers. Nevertheless reminders matters more than you realize, over 80% of responses to a dedicated/listed customer survey come within the next 24 hours of sending out an email invitation. Sometimes your invitation got pushed away and will be simply forgotten. With that in mind think of that first reminder as doing your customer a favour by giving a short and friendly reminder. Having said that, you should only send your reminders to customers who have not completed the survey.
Reliability of your (collected survey) data goes hand in hand with the response rate of your survey. The trick is to get at least a 95% confidence in return. The smaller the population (customer group) the higher response rate/sample size is necessary. At the end of the day the response rate highly correlates with the initial strength of the organization's relationship with your customer. To boost your survey response rate you should use a customer friendly reminder process; a series of reminders could easily double up the response rate. See figure 4.
Figure 4. Response rate.