Basic Concepts of Statistics

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Introduction

     Statistics is about collection of information and its presentation and about drawing inferences from these. We come across facts and figures in the newspapers, Television and the radio. The numerical figures are called "the data". If we have to draw good inferences from information collected, it has to be presented properly. We shall now study how the data collected is tabulated.

Statistics

     The collection of data, its classification, tabulation and study is called Statistics.

Variable

     Quantities such as height, weight, age, amount can have several different values. Quantities which can assume different numerical values are called variables. Variables are of two types: (a) Continuous (b) Discrete.

Tabulation of Data

     Consider Standard IX of a school. There are four divisions in this class. Standard IX-A has 10 girls and 12 boys. Standard IX-B has 6 girls and 20 boys. Standard IX-C has 18 girls and 12 boys. Standard IX-D has 16 girls and 24 boys.

Frequency Distribution

     The number which tells us how many times a particular data appears is called the frequency. For example, 2 marks have been scored by five students which means marks 2 occurs five times. Therefore, the frequency of score 2 is five. Similarly, the frequency of marks 5 is three because three students scored five marks. The data so distributed is called frequency distribution and the tabular form is called frequency distribution table. There are two types of frequency distribution: (a) Inclusive (b) Exclusive.

Summary

     1. Inclusive type of frequency distribution can be converted into exclusive type by extending the class limits by 0.5.

     2. Class width is the difference between the actual limits of any class.

     3. Class mark is the mid point of each interval.