BB cream is promoted as an all-in-one facial cosmetic product to replace serum, moisturizer, primer, foundation and sunblock. It can be worn alone as a tinted moisturizer, over serum and moisturizer as a regular foundation, and under powder, depending on the desired amount of coverage. 1  1 History.  2 Formulations.
Definition. Naturalistic observation is research that involves studying the subject of interest in its own environment, as it would occur in day-to-day life. The subject of interest may be human or non-human or it can be the behavior of living things or the interactions of non-living things with their environment.
A cohort study can delve even further and divide a cohort into sub-groups, for example, a cohort of smokers could be sub-divided, with one group suffering from obesity. In this respect, a cohort study is often interchangeable with the term naturalistic observation. There are two main sub-types of cohort study, the retrospective and the prospective cohort study.