Bill Selman wrote a great post on the importance of research triangulation. If you have trouble making the case for qualitative research in a company smitten with “big data”, show them Why Do We Conduct Qualitative User Research? (emphasis mine):

There is no one research method that satisfies answering all of our questions. If the questions we are asking about user behavior, attitudes, and beliefs are based solely on assumptions formed in our homophilic bubble, we will not generate accurate insights about our users no matter how large the dataset. In other words, we only know what we know and can only ask questions framed about what we know. If we are measuring, we can only measure what we know to ask. Quantitative user research needs qualitative user research methods in order to know what we should be measuring and to provide examples, theories, and explanations. Likewise, qualitative research needs quantitative research to measure and validate our work as well as to uncover larger patterns we cannot see.