Class 7 Notes - Data Handling
1. Introduction to Data Handling
Data handling is the process of collecting, organizing, representing, and interpreting information (data) to draw conclusions or make decisions. In Class 7, students learn to manage data using various methods and graphical representations.
2. Collection and Organization of Data
- Data Collection: Gathering information through surveys, experiments, or observations.
- Raw Data: Data as collected, not yet organized.
- Organization: Arranging data in tables or lists for better understanding.
3. Frequency Distribution
Frequency is the number of times a particular value appears in a data set. Data can be organized in a frequency distribution table to make it easier to interpret.
Example: Number of books read by students in a week: 2, 3, 2, 5, 3, 2, 4
Frequency Table:
| Books Read | Frequency |
|---|
| 2 | 3 |
| 3 | 2 |
| 4 | 1 |
| 5 | 1 |
4. Bar Graphs
Bar graphs are used to represent data visually using bars of different heights. Each bar represents a category and its frequency.
Example: Favorite fruits of students (Apple: 5, Banana: 3, Orange: 4, Mango: 2)
5. Double Bar Graphs
Double bar graphs are used to compare two sets of data side by side.
Example: Number of boys and girls in different classes.
6. Circle Graph (Pie Chart)
A circle graph or pie chart shows data as sectors of a circle. Each sector represents a part of the whole.
Example: Distribution of time spent on activities in a day.
7. Mean, Median, and Mode
- Mean (Average): Sum of all values divided by the number of values.
- Median: The middle value when data is arranged in order.
- Mode: The value that appears most frequently.
Example: Data: 2, 3, 3, 5, 7
Mean = (2+3+3+5+7)/5 = 4
Median = 3
Mode = 3
8. Chance and Probability (Introduction)
Probability is the measure of how likely an event is to occur. It ranges from 0 (impossible) to 1 (certain).
Example: Probability of getting a head when tossing a coin = 1/2
9. Word Problems
- In a survey of 30 students, 12 like cricket, 10 like football, and 8 like basketball. Represent this data using a bar graph.
- The marks obtained by 5 students are: 78, 85, 90, 85, 92. Find the mean, median, and mode.
- Draw a pie chart to show the distribution of time spent on study, play, and sleep in a day (6 hours, 4 hours, 14 hours).
10. Common Mistakes
- Not organizing data before analysis.
- Misreading bar heights in bar graphs.
- Confusing mean, median, and mode.
- Forgetting to label axes in graphs.
11. Practice Exercises
- Make a frequency table for the following data: 4, 5, 4, 6, 5, 4, 7, 5, 6.
- Draw a bar graph for the number of students in four houses: Red (10), Blue (15), Green (12), Yellow (8).
- Find the mode of the data: 2, 4, 4, 5, 6, 4, 7.
- What is the probability of getting a 3 when rolling a dice?
12. Summary
- Data handling involves collecting, organizing, and interpreting data.
- Data can be represented using tables, bar graphs, and pie charts.
- Mean, median, and mode are measures of central tendency.
- Probability helps in predicting chances of events.