What is the definition of a cross-sectional study?
A cross-sectional research is used to draw conclusions about a population at a certain point in time. The goal of these research project is not to follow up with the participants, but to gather data once and for all. When the researcher repeats the cross-sectional study with subsequent surveys, he does not use the same sample, but rather a different one. The investigator can ask inquiries of the entire population of interest or a subset of that group if it is too large.

In cross-sectional investigations, data collecting is important.
Any data gathering method, such as a questionnaire, interview, or observation, can be used by the investigator. An elementary school teacher, for example, believes that eating a protein-rich breakfast encourages students to be more active at school. She can send a questionnaire to her students' parents, asking them to fill it out and return it to her, so she can find out what they eat for breakfast and compare it to their children's activity and involvement in school. This will assist her in determining if her theory is correct or incorrect. In a cross-sectional research, the survey is typically easy, and no baseline data is obtained, therefore no follow-up is required. The inquiries are typically straightforward, and the investigator has no control over the outside influences.

The distinction between cross-sectional and longitudinal research
In cross-sectional research, the data is collected all at once, and the investigator can use whatever data collecting method that is most appropriate. This research will not be as generalizable as previous research. If it is more convenient, the investigator can apply an appropriate sampling procedure and gather data from the entire population of interest, or he can draw a sample. In longitudinal research, on the other hand, the investigator gathers data once and then repeats the same survey from the same population numerous times over a period of time. Longitudinal studies are used to compare outcomes and see how they have changed over time.

Advantages
In the social sciences, medical sciences, and economics, these investigations can be carried out on a regular basis. They do not require as much time as other types of investigations and can provide results. These studies provide useful information to a group of individuals, and hypothesis testing may be carried out on a small scale in a short period of time.

Disadvantage
The biggest drawback is that it does not produce as much generalizable data as other types of investigations. These investigations capture a single moment in time and do not give before-and-after data or outcomes. We cannot be certain that the results are actually representative, and the cause-and-effect link cannot be established.