At first glance, the two question types appear very similar. In both questions, your customers can choose from a variety of answers, either one answer or multiple, depending on your settings.
Single Select measures primary motives
Multiple Choice measures factor diversity
Which question type you choose depends on what exactly you want to achieve with the question.
Is your goal to prioritize causes? Then we recommend the Single Select question. This way you find out what is most important to your customers, what the main reason is why they, for example, do not complete a purchase, cancel a booking, or feel uncomfortable in the team. The answers are not distorted or diluted by multiple selection, but provide you with a clear hierarchy.
Do you want to understand relationships? Then we recommend Multi Select. This allows the reality of complex decision-making processes to be better represented. You can better recognize patterns and, based on this, formulate and test hypotheses for A/B tests.
If you want clear prioritization but still want to know all the reasons, you can ask two-stage questions. In this case, you first ask a Single Select question and then a free-text question. This way you find out whether other reasons also played a role, without distorting your initial results.