You will learn:
What is Data?
Data is a collection of facts such as values or measurements. We can also say that Data is a systematic record of a particular quantity. Data is the base of all operations in Statistics. Data represents facts and figures that can be used for further analysis or surveys.
Let's take an example:
Sammy was making a list for a picnic. He wrote: 'Ann, Susie, Madison and Christy like Pizza; Mac, Jim and John like Burger......'. His elder sister Mary, ask him to make a table as then it will be easier to see the likes and order food items quantity accordingly.
So Sammy called out the names and their choice of food and Mary started marking this in a table. Later she added up the marks for food ordering.
| Food Item |
How many like it. (each line denotes a child who is going for picnic) |
Number to order |
| Pizza |  |
4 |
| Burger |  |
6 |
| Sandwich |  |
7 |
Here slanting line represents the fifth child.
This table is a collection of facts and numbers. It tells us facts like 'how many Sammy's friends like Pizza'. So we can say that the table has data on what Sammy's friends like to eat in a picnic.
Let's take another example. The below table lists games the students of Grade II in your school are interested to play.
| Games |
Number of students O = 2 students |
| Football | O O O O |
| Badminton | O O |
| Basketball | O O O O O O |
| Tennis | O O O O O |
The above Graph or chart shows numerical information using symbols or icons to represent the data set. Such a pictorial representation of data is called a Pictograph.
From above pictograph we know the following:
A bar graph or Bar chart is another way of representing information or data. A Bar chart presents data with rectangular bars with heights or lengths proportional to the values that they represent. The Bars can be plotted horizontally or vertically.
Let us draw a Bar chart that displays the above pictograph data. On the graph paper mark games on the X-axis and the number of students on the Y-axis.
A line graph or Line chart is used to visualize the value of something over time. It can be drawn on a graph paper with the X and Y-axis. Let us plot a line graph using the below data:
The below table gives a daily average temperature of Charlotte city, recorded for 5 days in degrees Fahrenheit.
| Day |
Temperature(in °F) |
| 1 | 43°F |
| 2 | 53°F |
| 3 | 50°F |
| 4 | 57°F |
| 5 | 60°F |
Take Day on X-axis and Temperature on Y-axis. Determine the scale for both the axis and plot the points. Join the points with a line.
The Pie chart represents data in a circular graph. It is used when we need to see the proportion or percentage between categories by dividing the circle into proportional segments. Let us understand this using an example.
The following table shows the percentage of people in a locality with blood types. This data is gathered for a locality consisting of 200 people.
| Blood Group | Total number of people |
People in % [Total number of people∕200 × 100] |
| B | 80 | 40% |
| A | 40 | 20% |
| O | 60 | 30% |
| AB | 20 | 10% |
To draw a pie chart find a central angle for each component using the formula : (% value of component∕100) × 360. Using this formula, we derive each segment's central angle as:
| Blood Group | People in % | Angle |
| B | 40% | 144° |
| A | 20% | 72° |
| O | 30% | 108° |
| AB | 10% | 36° |
Draw a circle of any radius and then draw a horizontal radius. Starting with a horizontal radius makes central angles corresponding to the values of the respective components.
There are many other charts that you can use to represent the data like Histogram, Scatter plot, Bubble chart, etc.
