To choose the right techniques.

I always have encouraged other researchers to combine techniques according to the goals and the current stage of the Product development lifecycle.

This is a fact: the information you need to move forward changes during the lifecycle of your product.

To define a strategy and start building a solution, exploratory research with a generative approach is primary (orange dots). As the product evolves, it becomes more tangible. Therefore its validation becomes more relevant (pink dots).

Let's say you have an idea for a product and interview people to validate it. Starting with questions about the solutions they are using, informs you about adoption trends and good practices.

It can be the other way round too. Imagine that you want to know if that new functionality is understandable enough. Starting the usability tests with a brief interview will put the end-users in a comfortable area of knowledge before performing the tasks. At the same time, you understand their real goals, helpers and difficulties.

Combined studies are projects with both exploratory purposes and product evaluative goals. They provide more depth to the observations and are highly recommended.