# CLASS-9INTRODUCTION OF FREQUENCY DISTRIBUTION

FREQUENCY DISTRIBUTION

INTRODUCTION

In various fields, we need information in the form of numerical figures which is to be called or considered as data. These data may be related to the marks obtained by the pupils of a class in a certain examination; the weights, heights, ages, and many more, of pupils in a class, the monthly wages earned by workers in a factory, the population of a city, or the profits of a company during last few years, marks obtained by students in a class or school, etc. Evaluation of such data helps analysts study the various growth patterns and formulate future targets or policies or derive certain inferences.

Data

The word “data” means a set of given or obtained facts in numerical figures. It is only data.

Statistics

It is the science which deals with the collection, presentation, analysis, and interpretation of numerical data where analyst can make the future planning or strategy. In singular form, statistics is taken as a subject and in plural form, statistics means data.

Fundamental Characteristics of Data

i)       Numerical facts alone form data. Qualitative characteristics, like honesty, poverty, etc., which cannot be measured numerically and in a single word it is impossible to present as data because these does not form any data.

ii)       Data are aggregate of facts, we need to take various facts from various condition of same incidence. A single observation does not form data.

iii)      Data collected for a definite purpose may not be suitable for another purpose.

Types of Data

i)    Primary Data – The data collected by the investigator himself with a definite plan in mind are known as “primary data”.

ii)   Secondary Data – The data collected by someone, other than the investigator, are known as “secondary data”

Variable

A quantity which can take different values obtained from different objects of a same or different class is called a variable. Examples : Height, age, and weight of pupils in a class are three variables. If we denote them by x, y, are z respectively, then values of x give the heights of the pupils, the values of y give the ages of the pupils and the values of z give the heights of the pupils.

Continuous and Discrete Variables

Variables are two types :

i)    Continuous Variable – A variable which can take any numerical value within a certain range is called a “continuous variable”.

Examples – a) Wages of worker in a factory

b) Heights of people in a group

c)  Commission of employee in a office

d) Weight of student in a class

ii)    Discontinuous (or Discrete) variable : A variable which cannot take all possible values between two given values, is called a “discontinuous or discrete” variable.

a)      Number of members in a family

b)      Number of workers in a factory

Such variables cannot take any value between 1 & 2, 2 & 3, etc.

Important Terms

Range : The difference between the maximum and minimum values of a variable is called its range.

Variate :  A particular value of a variable is called “variate”

Presentation of Data : Putting the data in condensed form in the form of a table, is known or considered as “presentation of data”

Frequency : The number of times an observation occurs or happens is called its “frequency”.

Frequency Distribution : The tabular arrangement of data showing the frequency of each observation is called its “frequency distribution”.