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