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.
What is a Cohort? The focus of a panel study is a group of people who have a common attribute, experience or characteristic in a particular time period. This group is called the cohort. People that share the fact of being born on the same day, month, year or era may belong to a birth cohort.