Understanding how a Study is designed for a Statistical Analysis is essential to better understand the quality of the results or findings which are claimed by the study.
In this type of study one measures or surveys members of a sample without trying to affect the members or manipulating the variables.
Researchers do not impose any kind of treatment or restriction to the group nor do they randomly assign the subjects to a group. There is basically no manipulation of the environment in which the subject occurs. This could show a relationship between variables but it may not be a causal one. Evidence provided by this type of a study is generally weak to prove a causal relationship.
These studies are less expensive than experimental studies although the time required to complete these kind of studies could be of the order of several years or decades.
Randomly Assign a treatment to a group so that researchers can draw the causal conclusion. Here, we experiment and manipulate the environment of the subject to measure the response (dependent) variable.
Evidence provided by the experimental study is considered to be stronger than the observational study for detecting a causal relationship.
The experimental study involves two groups — experiment group and control group. Control group is the group in the study that does not receive treatment by the researchers.
Experimental Studies are closely monitored and are expensive. Although they are typically shorter than observational studies