The National Health and Nutrition Survey is an annual survey of the health status of the Republic of Korea's nationals living in all households in the Republic of Korea. The sampling of the National Health and Nutrition Survey was first conducted in the survey area consisting of an average of 60 households, with an average of 20 households sampled from each survey area, and then all family members in the sampled households were sampled. In order to extract the survey area, the variables of the characteristics of the survey area (ordinary family survey area, apartment survey area) and the area (Seoul, six wide area cities, Gyeonggi, Chung ching, Gyeongsang/Kiyowon, Jeollah/Jeju) are taken as the stratification variables. Please use the given information to define the following items.

Target population Sampling frame Sampling unit Observation unit Sampling Design