**A good understanding of statistics is to first understand the whole of a specific terminology.**

## Introduction

The statistical vocabulary is essentially that of demography. From the history of statistics, for centuries dedicated to the enumeration and description of populations, the terms that we will find are entirely linked to this history.

## The notion of population and individual

The first term is the **population**. It defines the set of data to be studied, it is also called field of study.

The population consists of all the values defined by a certain parameter:

- The people of France
- The size of people in Japan
- Cars produced by PSA
- …

An individual, usually rated X, is one of the constituents of the population. It is also called a statistical unit:

- One of the people of the French population
- The size of one of the people of the population of Japan
- One of the cars produced by PSA
- …

## The general terms of the statistics

#### Sample

In a statistical study, it is common for the entire population not to be observed. The observations and the data are a sample of the population.

#### Sample size

This is the number of individuals that the sample contains. We note n the size of the sample considered.

#### Statistical survey

It is the operation of observing (or measuring, or questioning…) All the people of the population.

#### Census

Survey in which the observed sample is in fact the entire population.

#### Survey

This is, on the contrary, an investigation in which the sample is a sample of the population.

#### Variable

It is a defined characteristic of the population. This application can be said to be quantitative (age, salary, size…), or qualitative (gender, socio-Professional category…).

#### Data

The data term is very much used in statistics. It refers to all the individuals observed (those of the sample), the set of variables considered and the observations of these variables on these individuals.

## Source** **

N. Bommena (2002) – Statistical reminders

A. Baccini (2010) – Basic descriptive statistics

Mr. Love (2010) – Introduction to descriptive statistics

D. Devika (2002) – Descriptive statistics

J. Levy (2010)-Web Math

CD4 3534-1 Standard

ISO/DIS3534-2 standard