12.3:
Observational Studies
Observational studies involve carefully monitoring or observing events without attempting to influence the outcome.
There are three types of observational studies. Prospective studies look at the future, retrospective studies look at the past, and cross-sectional studies measure outcomes in a specific time period.
So, finding out how many liters of fuel a car would need to travel for the next 500 kilometers would be a prospective study.
On the contrary, retrospective or case-control studies are carried out in the present based on past data.
For instance, a group of patients suffering from chronic obstructive lung disease was selected and asked about their smoking history. A significantly high number of patients with a smoking history indicates the possible association between tobacco smoke and the disease.
A survey conducted by an army research group on the state-wise recruitment of army personnel would be a cross-sectional study. Here, the study is done for a specific period to find the number of soldiers from each state among the total recruits.
12.3:
Observational Studies
Observational studies are a type of analytical study where researchers observe events without any interventions. In other words, the researcher does not influence the response variable or the experiment's outcome.
There are three types of observational studies – Prospective, retrospective, and cross-sectional.
Prospective Study
Prospective studies, also known as longitudinal or cohort studies, are carried out by collecting future data from groups sharing similar characteristics. One example of a prospective study would be assessing the effect of diet, exercise, and medication on heart disease among the residents of a specific city. Prospective studies are instrumental for medical researchers, especially in epidemiology. These studies allow scientists to observe the progression of a disease over time and compare the risk factors among subjects.
Retrospective Study
On the other hand, retrospective or case-control studies are conducted in the present but require researchers to collect data from the past. An example of such a study would be determining a relationship between tobacco smoke and chronic obstructive lung disease based on the smoking history of patients with chronic obstructive lung disease.
Cross-sectional Study
A cross-sectional study is one in which the data is collected and analyzed at a specific time. Evaluating the prevalence of cancer among people of different age groups, gender, social background, and geographical location is an example of a cross-sectional study.