Definition of statistics
Ands the art to make inferences and take out conclusions from imperfect data. Lyou data are generally imperfect in the sense that still when they possess useful information do not explain us the complete history. It is necessary to have methods that allow us extract information from the data observed to comprise better the situations that the same represent.
Some technicians of analysis of data are surprisingly simple to learn and use further of the fact that the mathematical theory that the sustentan can be very complex . All, still the statisticians, have problems when confronting us with listings of data. They exist a lot of statistical methods whose purpose is to help us to put of self-evident the excellent and interesting characteristics of our data that can be used in almost all the areas of the knowledge.
Descriptive statistics
The methods of the Descriptive Statistics or Exploratory Analysis of Data help to present the data of way such that project his structure. There are several simple and interesting forms to organise the data in charts that allow to detect so much the excellent characteristics like the unexpected characteristics. The another way to describe the data is resumirlos in one or two numbers that pretend to characterise the group with the lower distortion or lost of possible information
Data 
They are numbers that can be compared, analysed and interpreted. The field of the cual are taken the statistical data identifies  like population or universe.
It determines the method of appropriate and valid analysis and each method of statistical analysis is specific for a true type of data. The most important distinction is between numerical and categorical data.
Types of data
It calls  statistical variables to each one of the characteristics that can study of the population. They are they can be of two types:
•	Categorical or qualitative
The categorical variables result to register the presence of an attribute. Son Those in which the possible results are not numerical values. For example: colour of the peel, type of clothes preferred, place of veraneo, etc.
•	Quantitative
Those whose result is a number. A variable is numerical when the result of the observation or measurement is a number. They classify  in: 
To) Discreet: The variable only can take a true group of possible values. In general, they appear by conteo. Example: number of members of the home, number of surgical interventions, number of cases notified of one some pathology. 
b) Continuous: Generally they are the result of a measurement that expresses  in units. The measurements can take theoretically an infinite group of possible values inside a rank. In the practice the possible values of the variable are limited by the precision of the method of measurement or by the way of register. Examples: height, weight, pH, level of cholesterol in blood. 
The distinction between discreet and continuous data is important to decide which method of statistical analysis use, since there are methods that suppose that the data are continuous.
Presentation, tabulation and grafica of data
1.- Presentation
The presentation of statistical data constitutes in his different modalities one of the appearances of but use in the descriptive statistics. To split can visualise through the different half writings and television of massive communication the presentation of the statistical data on the behaviour of the main economic variables and social, national and international.
2.- Tabulation
The simplest way to present categorical data is by means of a table of frequencies. This table indicates the number of units of analysis that fall in each one of the classes of the qualitative variable
3.- Grafica
	The descriptive statistics or exploratory analysis of data offers ways to present and evaluate the main characteristics of the data through tables, charts and measured summaries. In this chapter will present simple forms of resumir and represent gráficamente conjoint of data. The aim to build charts is can appreciate the data like an all and identify his excellent characteristics. The type of chart to select depend of the type of variable that interest us represent by this reason will distinguish in the graphic presentation for categorical variables and for numerical variables