The primary objective example of an observational study design is the cross-sectional study design.However, it is challenging to infer causal links from cross-sectional research because this is a one-time evaluation of exposure and result.The researcher monitors the study to evaluate the exposure and the results after the participants have been chosen for it. 
     Cross-sectional designs are employed in clinic-based samples to determine the prevalence of illnesses and in population-based surveys.In contrast to case-control studies, where participants are chosen based on the outcome status, or cohort studies, where participants are picked based on the exposure status, cross-sectional study participants are picked solely on the basis of the study's inclusion and exclusion criteria.In a cross-sectional study, the researcher or investigator simultaneously assesses the study participants' exposures and outcomes.The prevalence of outcomes or exposures will be revealed by these kinds of designs, and we may utilize this knowledge to help construct the cohort research.In cross-sectional investigations, the prevalence of an illness can be estimated.