## Class 9 Statistics Chapter 14 – Explanation with Examples

Statistics is a part of Mathematics that study the basic process of collecting, organizing, analyzing, interpreting the data and information and presenting them in the form of graphs and so on.

**There are many basic terms to learn in Statistics such as:**

**Primary Data:**Primary data is used to term the information that are gathered or collected by the primary investigators themselves for their specific work or task.**Secondary Data**: When it comes to information collected not by the primary investors themselves but rather from other sources that had already saved the information, then such data gathered or collected are termed as secondary data.**Raw Data:**Raw data are the data collected directly from a source without being processed by human for further application or use.- This can include data collection of marks scored by students in various subjects like for example, data collection of marks of science of 10 students is given below:
- 55 70 80 73 99 100 68 75 85 95. The data collected can be said to be in raw form or is called raw data.

**Range:**The range can be defined as highest value of the data collected minus the lowest value in the collected data.- Range = Highest value(HV) – Lowest value (LV)

**Ungrouped Frequency Distribution (UFD) Table:**An ungrouped frequency table is a table that represent data in a form that can be easily understood. For example, if we consider the marks in Social studies obtained by 30 students of class VIII of a particular school are as follows:

70 | 20 | 92 | 36 | 72 | 40 | 95 | 50 | 88 | 60 |

10 | 40 | 60 | 92 | 56 | 70 | 36 | 60 | 70 | 88 |

50 | 36 | 70 | 40 | 80 | 60 | 50 | 40 | 56 | 92 |

The table shown in the figure is called the UFD table or just a frequency distribution table. The number of students who have the same marks is called the frequency. Example, the number of students who scored 60 is 4. Hence, 4 is the frequency of 60 marks.

**Grouped Frequency Distribution (GFD) Table:**The GFD table on the other hand is different from UFD table as:- GFD is used to represent data of large amount by condensing it to smaller groups. The grouping of such data is called a class.
- In a class, the least number is called the lower-class limit whereas the greatest class’ number is known as the upper-class limit. For example, in a 20-50 class 20 is the lower-class limit and 50 is the upper-class limit.
- A class interval is said to be the upper-class limit minus the lower-class limit.
- There is also a term class mark which is the mid-point of a class.

Example of a GFD table: During world Environment day, 100 schools of a certain place were asked to plant 100 plants each. A survey was conducted after 1.5 months to see how many plants survived and the data were recorded as:

20 | 65 | 38 | 64 | 40 | 30 | 45 | 31 | 91 | 37 |

42 | 74 | 43 | 80 | 61 | 83 | 81 | 66 | 81 | 89 |

35 | 90 | 55 | 36 | 81 | 59 | 80 | 57 | 65 | 79 |

72 | 67 | 81 | 78 | 69 | 84 | 83 | 39 | 80 | 90 |

34 | 92 | 25 | 89 | 85 | 96 | 46 | 88 | 49 | 78 |

41 | 52 | 44 | 62 | 83 | 29 | 88 | 67 | 88 | 35 |

70 | 76 | 93 | 78 | 37 | 79 | 97 | 85 | 95 | 61 |

69 | 89 | 39 | 63 | 45 | 68 | 82 | 98 | 64 | 99 |

32 | 53 | 86 | 95 | 82 | 31 | 84 | 32 | 98 | 72 |

40 | 60 | 52 | 61 | 50 | 62 | 47 | 51 | 63 | 49 |

The data can be represented in a tabular form as:

**Graphical Representation of Data:**Data can be represented in the form of bar graphs, histogram, frequency polygon and so on.- Bar graphs: A bar graph contains x and y axis and is used to represent data in a pictorial way.
- Histogram: Another graphical representation of data is a histogram which represent data of GFD with continuous classes.

**Mean**:

**Median:**From the given number of observations the median is the value which divides it into two parts the higher half and the lower half.**Mode:**The value of the collected data or the observation that frequently occurs is called the mode i.e., the value one having maximum frequency.