Often called quartz topaz, citrine topaz, or topaz, all of which are misleading. It is yellow, amber, to amber brown. While a pleasing stone in terms of colour, and fairly durable, citrine is slightly softer and has less brilliance than precious topaz.
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. The major difference between the two is that the retrospective looks at phenomena that have already happened, whilst the prospective type starts from the present. . The retrospective case study is historical in nature.
Observational studies are ones where researchers observe the effect of a risk factor, diagnostic test, treatment or other intervention without trying to change who is or isnât exposed to it. Cohort studies and case control studies are two types of observational studies. Cohort study: For research purposes, a cohort is any group of people who are linked in some way. For instance, a birth cohort includes all people born within a given time frame.