You've completed your survey and have deployed it out into the wild, but you're not getting the number of responses you had hoped for. Survey length is the number one reason for respondent drop out, but another reason may be you have forced customers to answer the wrong questions.
The general rule of thumb is you want every answer on every single one of your customer survey questions to be required questions. If your incentive is good enough, it shouldn't matter whether the question is open ended or the survey is long, the customer will complete it.
There are of course some exceptions or situations to keep in mind if you don't have the best customer incentive.
Allow users to skip questions on sensitive topics
According to research from Université du Luxembourg in Germany, if a survey participant is forced to answer questions they deem sensitive, they may drop out and abandon the survey. Worse, they had a higher tendency to give a neutral and inaccurate answer, skewing your results.
The questions used in the study were about being a victim of a crime or the participant had ever evaded taxes. This is much more extreme than a typical customer survey, but you can apply this logic to questions like "What is your household income?"
Allow users to skip questions asking them to give their email addresses and other contact information
When you forcing customers to leave their email with you may make them uncomfortable. Customers we've talked to in the past have said they fear getting their email spammed or just don't want to receive mail from you at this time.
Obviously, if the main goal of your survey is to gather email addresses and personal information, leave these types of questions in. You'll most likely need to spend a bit more on valuable incentives to convince hesitant customers to hand over their information.
Certain open-ended questions
We've talked about the power of open-ended questions in the past before and one aspect we warned about was the intimidating effect they have on customers. These questions are important for you as a business, but make sure the customers have an easy way of answering them if you're going to make them required.
For example, if you want to reward employees who made a wonderful impression on customers, you may want to put the question, "What was the name of the associate who helped you today?" This is a fine question to ask, but make it skip-able!
If a customer has the possibility to not remember the answer to an open-ended question, it's more beneficial to add a skip button. Rather have blank answers than wrong answers.