Data Handling and Visualization, CBSE Classes 6-8

Data is everywhere around us. Every time you check cricket scores, read a weather report, or look at your exam results, you are using data. In CBSE Classes 6-8, you will learn how to collect, organize, analyze, and present data in meaningful ways. This guide covers everything you need to know.

What is Data?

Data is a collection of facts, numbers, or information. By itself, raw data may not mean much. But when we organize and analyze it, data tells us important things.

Example of raw data: 85, 92, 78, 65, 90, 73, 88

This is just a list of numbers. But if we know these are your test scores, the data becomes meaningful. We can find your highest score (92), lowest score (65), and average score (81.6).

Types of Data

Type	Description	Examples
Numerical (Quantitative)	Data that can be measured with numbers	Height, weight, marks, temperature
Categorical (Qualitative)	Data that describes qualities or categories	Color, city, gender, favorite sport

More About Data Types

Numerical data can be further divided into:

• Discrete - Countable whole numbers (number of students: 35, 40, 42)
• Continuous - Can take any value in a range (height: 152.5 cm, temperature: 36.7)

Categorical data can be:

• Nominal - No natural order (colors: red, blue, green)
• Ordinal - Has a natural order (ratings: poor, good, excellent)

Collecting Data

Primary Data

Data that YOU collect yourself for the first time.

Methods:

1. Surveys/Questionnaires - Ask questions to people
2. Observations - Watch and record what happens
3. Experiments - Test something and record results
4. Interviews - Talk to people one-on-one

Secondary Data

Data that was collected by SOMEONE ELSE and you use it.

Sources:

1. Books and newspapers
2. Websites
3. Government reports
4. Census data
5. Research papers

Feature	Primary Data	Secondary Data
Collected by	You	Someone else
Freshness	Current	May be old
Cost	More expensive	Less expensive
Time	Takes more time	Available quickly
Accuracy	Controlled by you	May have errors

Organizing Data

Tally Marks

Tally marks are used to count occurrences. Every fifth mark crosses the previous four.

Example: Favorite fruits of 20 students

Fruit	Tally Marks	Count
Apple
Banana
Mango
Orange
Total		20

Frequency Table

A frequency table shows how many times each value appears.

Example: Marks of 15 students in a test

Raw data: 8, 7, 9, 6, 8, 10, 7, 8, 9, 6, 8, 7, 9, 10, 8

Marks	Frequency
6	2
7	3
8	5
9	3
10	2
Total	15

Grouped Frequency Table

For large ranges of data, we group values into intervals called class intervals.

Example: Heights of 20 students (in cm)

Height (cm)	Frequency
130-140	3
140-150	5
150-160	7
160-170	4
170-180	1
Total	20

Data Visualization (Charts and Graphs)

Data visualization means showing data in a visual form like charts and graphs. Pictures make data easier to understand.

1. Bar Graph

A bar graph uses rectangular bars to show data. The height or length of each bar represents the value.

When to use: Comparing different categories.

Example: Favorite sports of students

Sport	Students
Cricket	15
Football	10
Badminton	8
Tennis	5
Basketball	7

In a bar graph, each sport gets a bar. Cricket has the tallest bar (15), Tennis has the shortest (5).

Rules for bar graphs:

• Bars must have equal width, Equal spacing between bars, Label both axes, Give a title to the graph, Bars can be vertical or horizontal

2. Pie Chart

A pie chart is a circular chart divided into slices. Each slice represents a proportion of the whole.

When to use: Showing parts of a whole (percentages).

Example: How Priya spends her 24-hour day

Activity	Hours	Percentage
School	8	33.3%
Homework	3	12.5%
Play	2	8.3%
Eating	2	8.3%
Sleep	8	33.3%
Other	1	4.2%

How to calculate the angle for each slice:

Angle = (Value / Total) x 360

• School: (8/24) x 360 = 120 degrees, Sleep: (8/24) x 360 = 120 degrees, Homework: (3/24) x 360 = 45 degrees, Play: (2/24) x 360 = 30 degrees, Eating: (2/24) x 360 = 30 degrees, Other: (1/24) x 360 = 15 degrees

3. Line Graph

A line graph shows data as points connected by lines. It is used to show how data changes over time.

When to use: Showing trends over time.

Example: Average temperature in Delhi over 6 months

Month	Temperature (C)
January	14
February	17
March	23
April	30
May	35
June	34

In a line graph, you plot each month's temperature as a point and connect the dots with lines. This shows the temperature trend, rising from January to May and slightly dropping in June.

4. Pictograph

A pictograph uses pictures or symbols to represent data. Each picture represents a certain number of items.

When to use: Making data fun and easy to read, especially for younger audiences.

Example: Books read by students (each book icon = 5 books)

• Aman: 4 icons = 20 books, Priya: 3 icons = 15 books, Rahul: 5 icons = 25 books

Always include a key that shows what each picture represents.

5. Histogram

A histogram is similar to a bar graph but is used for continuous data with class intervals. The bars touch each other (no gaps).

When to use: Showing frequency distribution of continuous data.

Marks Range	Students
0-20	3
20-40	7
40-60	12
60-80	15
80-100	8

Choosing the Right Chart

Type of Data	Best Chart
Comparing categories	Bar graph
Parts of a whole	Pie chart
Change over time	Line graph
Simple comparisons for kids	Pictograph
Continuous data distribution	Histogram

Basic Statistics

Mean (Average)

The mean is the sum of all values divided by the number of values.

Mean = Sum of all values / Number of values

Example: Marks: 85, 92, 78, 65, 90

Mean = (85 + 92 + 78 + 65 + 90) / 5 = 410 / 5 = 82

Median

The median is the middle value when data is arranged in order.

Example: 65, 78, 85, 90, 92

Median = 85 (the middle value)

For even number of values, median = average of the two middle values.

Example: 65, 78, 85, 90

Median = (78 + 85) / 2 = 81.5

Mode

The mode is the value that appears most frequently.

Example: 7, 8, 8, 9, 8, 7, 10

Mode = 8 (appears 3 times)

Range

The range is the difference between the highest and lowest values.

Range = Highest value - Lowest value

Example: 65, 78, 85, 90, 92

Range = 92, 65 = 27

Spreadsheet Basics

A spreadsheet (like Google Sheets or Microsoft Excel) is a tool for organizing and analyzing data.

Key Spreadsheet Terms

Term	Description
Cell	A single box in the spreadsheet (e.g., A1, B3)
Row	A horizontal line of cells (numbered 1, 2, 3...)
Column	A vertical line of cells (labeled A, B, C...)
Formula	A calculation (starts with =)
Function	A built-in formula (SUM, AVERAGE, MAX, MIN)

Common Spreadsheet Functions

Function	Purpose	Example
=SUM(A1:A5)	Adds values	Sum of cells A1 to A5
=AVERAGE(A1:A5)	Finds mean	Average of cells A1 to A5
=MAX(A1:A5)	Finds highest	Highest value in A1 to A5
=MIN(A1:A5)	Finds lowest	Lowest value in A1 to A5
=COUNT(A1:A5)	Counts numbers	Count of numbers in A1 to A5

Creating Charts in a Spreadsheet

1. Enter your data in the spreadsheet
2. Select the data you want to chart
3. Click Insert > Chart
4. Choose the chart type (bar, pie, line)
5. Add a title and labels
6. Customize colors if needed

Practice Activities

Activity 1: Collect and Visualize Data

Conduct a survey in your class:

• Ask 20 classmates about their favorite subject, Create a tally chart, Make a frequency table, Draw a bar graph, Draw a pie chart

Activity 2: Analyze Data

Using these test scores of 10 students: 75, 82, 90, 65, 88, 70, 95, 78, 84, 73

1. Find the mean
2. Find the median
3. Find the mode
4. Find the range
5. Create a frequency table
6. Draw a bar graph

Activity 3: Spreadsheet Practice

Enter your monthly test marks in a spreadsheet:

1. Use SUM to find total marks
2. Use AVERAGE to find your average
3. Use MAX and MIN to find highest and lowest
4. Create a line graph showing your performance over months

Key Takeaways

• Data is facts and numbers that help us understand the world
• Primary data is collected by you; Secondary data is from other sources
• Tally marks and frequency tables help organize data
• Bar graphs compare categories; Pie charts show parts of a whole
• Line graphs show trends over time; Pictographs use pictures
• Mean = average; Median = middle value; Mode = most frequent; Range = highest minus lowest
• Spreadsheets help organize, calculate, and visualize data, Always choose the right chart for your data type