Statistics

The first step in doing a statistical study is usually to obtain raw data. As an example, suppose that a researcher wants to know the number of female African-Americans in each of six age groups (1-19; 20-29; 30-39; 40-49; 50-59; and 60+) in the United States. One way to answer that question would be to do a population survey, that is, to interview every single female African-American in the United States and ask what her age is. Quite obviously, such a study would be very difficult and very expensive to complete. In fact, it would probably be impossible to do.

A more reasonable approach is to select a sample of female African-Americans that is smaller than the total population and to interview this sample. Then, if the sample is drawn so as to be truly representative of the total population, the researcher can draw some conclusions about the total population based on the findings obtained from the smaller sample.