**Chapter Notes and Summary**

• **Data : **word data means information in form of numerical figures. e.g., marks obtained by 10 students of a class in a monthly test are given below :

27, 21, 35, 41, 45, 15, 18, 46, 47, 28.•

**Raw data :**Data obtained in original form is called raw data.

**30, 35, 45, 29, 39, 54.**

e.g., ages (in years) of 6 teachers in a school are :

e.g., ages (in years) of 6 teachers in a school are :

**The given data related to ages of 6 teachers in a school**

**•**

**Array :**Arranging numerical figures in an ascending or a descending order is called an array. e.g., data in

**an ascending order.**

**i.e., 1, 1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 6, 6.**

**and data in an descending order**

**i.e, 6, 6, 5, 5, 4, 4, 4 3, 3, 3, 2, 2, 1, 1, 1.**

**•**

**Tabulation of data :**Arranging data in a systematic tabular form is called tabulation or presentation of data.

**•**

**Observations :**Each numerical figure in a data is called an observation.

**•**

**Frequency of an observation :**number of times a particular observation occurs is called its frequency.

**•**

**Statistics :**It is science which deals with collection, presentation, analysis and interpretation of numerical

**data.**

**•**

**Pictograph :**representation of an information through pictures is called a pictograph.

**•**

**Bar graph :**In a bar graph, bars (rectangles) of uniform width are created horizontally or vertically with equal

**spacing between them.**

**• In a bar graph, heights (or length) of bars represent given number.**

**• Bar ( ) represented to each observation in data is called tally marks.**

**• Tally marks are in group of 4 ( ). 5th mark makes a bundle ( ). Tally marks help in counting large**

**number.**

**• Using tally marks, data can be arranged in a tabular form and particular information can be obtained from**

**data quickly.**