The database commonly uses an index range scan to access selective data. The selectivity is the percentage of rows in the table that the query selects, with 0 meaning no rows and 1 meaning all rows. Selectivity is tied to a query predicate, such as WHERE last_name LIKE 'A%', or a combination of predicates.
Types of Distribution: Intensive, Selective and Exclusive Distribution. Some of the important types of distribution in international market are 1. Intensive 2. Selective and 3. Exclusive distribution.
This sampling is carried out when the parameters of the entire population are not required. This type of sampling is easy, cheap and quick but not accurate. Non-probability sampling can be classified into 5 types. Convenience sampling: In this sampling subjects are selected on the convenience of the researcher.