In our daily life we often must examine some given material. We examine fruits before we purchase them, and we examine any item before we purchase it. Even children check sweets, pencils, bats, erasers and other items when they have to purchase them. This approach is applied to different fields of life. Products in factories are inspected to ensure the desired quality of the products. Medications are manufactured on a commercial scale when their effects have been tested on a sample of patients. Different fertilizers are tested on agricultural plots and different foods are tested on animals. Small dams are constructed as a sample in laboratories to study the life and other characteristics of big dams before they are actually constructed. Some color may be applied as a sample on a wall, on a door or clothing, etc., and the result of the color is observed before being applied on a large scale. Cement, steel and bricks are examined as a sample before being used in different places.
This process of inspection is very widespread and is commonly used on various occasions. However, this job is never done on a very large scale. This process is carried out on a small scale. On the basis of a small study, we make an opinion about the entire material under study.