When conducting a comprehensive literature search, what is the primary purpose of deliberately including epidemiological or statistical sources regarding the prevalence of a behavior?

A researcher is planning a study on the effects of sleep deprivation on exam performance among college students. During her literature search, she includes a national health survey reporting that 65% of college students regularly sleep fewer than seven hours per night. The primary purpose of including this source is to establish the real-world significance and broader importance of her research topic.