Definition of Variable,Constant,Discrete variable,Continuous variable,Qualitative variable,Quantitative variable ,Observation,Population,Sample,Survey?

Variable:

A measure quantity which can vary from time to time, place to place, person to person is called variable e.g. height, weight, ages, prices etc. variable are usually denoted by capital letters such as X, Y, Z etc.

Constant:

Any quantity which can assume only one value is called constant. Example of constants are  = 3.14159 e = 2.71828. A constant is usually denoted by first letter of alphabet e.g. a, b, c etc.

Discrete variable:

A variable which can take finite or countable number of values is called discrete variable e.g. number of children in a family, number of road accidents, number of rooms in a house etc. In discrete variable the values are taken by jumps or by breaks e.g. number of children in a family can be 0, 1, 2, 3…… etc.

Continuous variable:

A variable which can assume every possible value in the given range (interval) is called continuous variable. Height and weight of the individuals, height of mercury in thermometer, speed of a car etc. the values of continuous variables very without any gaps or jumps e.g. height of individual can be 62”, 62.3” 2.7” etc.

Qualitative variable:

A variable which be expressed numerically is called qualitative variable. OR a variable which cannot possess any unit of measurement is called qualitative variable e.g. intelligence, honesty eye clour etc.

Quantitative variable:

A variable which can be expressed numerically is called quantitative variable. OR a variable which can possess some units of measurements is called quantitative variable e.g. height can be expressed in inches centimeter, meters etc, weight can be expressed in kgs, grams etc.

Observation:

Any sort of numerical recording of information’s is called an observation or data. The observation may either be a physical measurement. Such as height, weight ages etc. OR answer to question such as yes or no etc.

Population:

The aggregate or totality of certain elements under study is called population. Total number of students in a college, total number of trees in a forest etc. is the examples of population.

Sample:

A small part of the population selected for the purpose of certain study is called sample. E.g. to diagnose the blood disease, a doctor takes a small part (few drops) of blood from patients body. Such a small part of blood is called sample.

Survey:

A planned and systematic process of collecting statistical data is called survey. There are two types of surveys i.e. census survey and sample survey.

1.                 Census survey:

A survey in which observations are made on each and every unit of the population is called census survey or population survey. The data obtained by recording the relevant information’s on each and every element of the population are called census data or population data.

2.                 Sample survey:

A survey in which information’s are collected by studying only small part of the population is called sample survey and the data obtained from sample survey is called sample data.