researchers want to know CV risk about African American populations but do not have data for every person.If a researcher wanted to learn whether being certain ethnicity increase a risk of particular disease, it would not be practical to study every individual from that ethnicity . Instead, the researcher might select a sample of the population. A sample is a smaller group of members of a population selected to represent the population. In order to use statistics to learn things about the population, the sample must be random. A random sample is one in which every member of a population has an equal chance of being selected. The most commonly used sample is a simple random sample. It requires that every possible sample of the selected size has an equal chance of being used.
In addition to the explanation by drjungly, the question literally states that they are using national census data. They aren't sampling data from a town/city, they are taking the entire US census data from 2000. This is population level data.
submitted by drjungly(15)
researchers want to know CV risk about African American populations but do not have data for every person.If a researcher wanted to learn whether being certain ethnicity increase a risk of particular disease, it would not be practical to study every individual from that ethnicity . Instead, the researcher might select a sample of the population. A sample is a smaller group of members of a population selected to represent the population. In order to use statistics to learn things about the population, the sample must be random. A random sample is one in which every member of a population has an equal chance of being selected. The most commonly used sample is a simple random sample. It requires that every possible sample of the selected size has an equal chance of being used.