A person wants to study a disease &;x&; and fat consumption. He obtained data for number of people affected with &;x&; from the government and the details of fat consumption from food industry. Type of study is

Ecological (correlations) study. Unit of study is population (results not applicable to individuals). Done in a small time frame. It is inferior to coho and case control. Reference: Park's textbook of preventive and social medicine,K.Park,21st edition,page no:59 & 22nd edition, pg no.60.