Before you design a system or product it's crucial to do your research on what your end users want and need, and there are few ways you can do this, including questionnaires, interviews and observations. Questionnaires are a great tool to use when you are trying to measure behaviour, attitudes, preferences, opinions, and intentions of a relatively large number of subjects. They're also a cost effective and quick way to collect large amounts of valuable data. Interviewing is another option, however this is time intensive and you won't be able to reach as many people as you can with questionnaires.

The benefit of interviews is that they are personal, creating opportunities for you to gain deeper insights. This is a great tool to use when you're trying to learn about a user's opinion of your product, system or service. The key to successful interviewing is to ask the right questions. You could use methods like interviewing to form personas or user journey maps. These tools help you to empathise with your users and put them at the heart of your design. 

Observations are another great way to do user research. By gathering data on how people are actually using your product, system or service you can make improvements to create a better UX. Observations should be intentional and goal-orientated. The benefits of observation are that it focuses on behaviour and not on reported sentiment. Okay, so to pull this all together doing research is critical if you want to ensure that your product, system, or service has the best possible UX. It is the best way to gain insights to what your end users want or need.

As you've seen, there are a few different kinds of user research you can conduct, and they all have different benefits. You should use as many of these as you think is necessary to get the best idea of how users feel about your product, service or system. If you make changes or design something based on effective research the chances are high that your customers will keep on coming back for more.