A coho study is -
Coho study is also known as incidence study. The cohos are identified prior to the appearance of disease under investigation. The study group so defined are observed over a period of time to determine the frequency of disease among them Ref: 25th edition, Park's Textbook of Preventive and Social Medicine, Page no. 83
An analytical study
A descriptive study
A corelational trail
An experimental study
Epidemiology