**What is Statistics?**

“The study of collection, presentation, analysis of data and drawing conclusion about parameter on basis of statistical inference is called Statistics”. Following is a block diagram that defines statistics:

All four terms mentioned in bold in the above block diagram are defined below:

“Any well-defined group of individuals/items/objects whose characteristics are to be studied is called Population”. For example,**Population:***students of a college*or*books in a library*.

**Parameter:**“Any quantity which defines the characteristic of whole population is called a Parameter”; it’s therefore the average of a population.

**Sample:**“A part of population is called a Sample”. Sample is a subset of population (universal set). In statistics, a sample is drawn to avoid calculations on a large population.

**Statistic: “**A characteristic of sample is called Statistic”. It is thus an average of a sample. Statistic is a singular word while statistics is plural.

**Types of Statistics:**

There are two types of statistics which are descriptive statistics and inferential statistics. In the definition of statistics; **collection, presentation and analysis** of data are *parts of descriptive statistics* whereas **drawing ****conclusion about parameter on basis of statistical inference** is a *part of inferential statistics*. Descriptive and Inferential Statistics are defined below:

**Descriptive Statistics: **It is a type of statistics that deal with organizing and summarizing data.

**Inferential Statistics: **It is a type of statistics that deal with using data you have collected to form conclusions.

**Data Collection & Sources of Data**

Data is necessary for statistical analysis and it is collected from two sources which are internal sources and external sources. Internal and external sources are mentioned below:

**Internal Sources:**

If information is available; then, we use internal sources for collecting data. Internal sources of data are internal reports of an organization. For instance, *a factory publishes its annual report on total production, total profit and loss, total sales, loans, wages to employees, bonus and other facilities to employees etc.*

**External Sources:**If desired information is not available; then, it is obtained from external sources which are primary sources and secondary sources. Primary and secondary sources are mentioned below:

**Primary Sources: **Primary sources of data are **sample survey** (*information is collected from a correspondent; its tool is questionnaire*) and **experimentation** either *fields like agriculture* or *labs* (*research sides/industries*). Data collected from primary sources is a primary data and it is defined as: ** **“Data collected by the investigator himself/herself for a specific purpose or from a primary source”. It is also called *First Hand Data*.

**Secondary Sources: **Secondary sources of data are **official sources** (*government sources*); for e.g. *ministries and departments*, **private sources** (*non-government sources*) for e.g. *magazines and newspaper*, **semi-private sources** and **unofficial sources**. ** **“Data already collected or taken from a secondary source is called a Secondary Data”. It is also called *Second Hand Data*. Secondary data may be used or unused, published or unpublished.

**Variable & Types of Variable**

**Variable: **“A characteristic of individuals of a population or of a sample which varies from individual to individual is called a Variable”. There are two types of variables which are mentioned below:

“Variable that cannot be specified in numbers; therefore, category has to be made for it is called a Categorical Variable”. For example:**Categorical or Qualitative Variable:***title of a book and blood group of a student*.

**Quantitative or Numerical Variable:**“Variable that can be specified in numbers is called a Quantitative Variable”. For instance:*number of pages in a book and weight of a student*. Quantitative variable has two subgroups which are defined below:

**Discrete Variable: “**A characteristic which is countable and can take on discrete values is called a discrete variable”. A discrete variable take limited numbers from 5-10 like 6, 8 and 10.**Number of siblings****in a family**,**number of tickets sold in cinema for a particular movie in a day**and**birth year of student**are some examples of discrete variable.**Continuous Variable:**“A characteristic which is measurable and can assume all possible values within a given range of values is called a Continuous Variable”; as between 5-10; some of which may be 5.6, 7.0 or 8.9. Some examples of continuous variable are**weight**,**pressure**and**mass**.