A database is a collection of data in secondary storage managed by a dedicated software system, called DBMS (System Management Databases). The data, therefore, are organized within the database. Each database in turn, is composed of one or more tables of data, based on which companies build their own reports.
Each table is composed of a series of rows and columns. They represent the records (in statistical terms such units), ie the individual representations. The columns, however, are the attributes , also known as fields or field and that the statistic defined as variables or characters. So for example if the company records in a table is the customer, the attribute is his name. The intersection of a record generates an attribute value, ie a mode that that particular character can take.
A data matrix is \u200b\u200ba set of statistical units and characters which can be derived from observed modes.
The contingency tables or frequency represent and analyze relationships between two or more variables, reporting the combined frequency of the variable. These tables are also referred to tables of association. Consider, for example, the two characters: age and city of residence. Otter as a way of numbers, which represent the age, and the names of cities, which represent the city of residence. You can also create pairs of modes, referring to the example, a person of 30 years who lives in Milan.
If you do this for all pairs of modes of association tables are built, they can be collected for any mode of two characters, how many units there are statistics that have the given characteristic.
These tables are not present in the database, but are derived from tables in the report by executing a count performed by the software.
It is then a report, or information of a statistical characterized by the 'size' and 'measure'.
0 comments:
Post a Comment