Line Charts, Bar Charts & Pictograms

Line Charts

A line chart is a graphical way to show how data changes over time. It is useful for spotting trends, patterns, and fluctuations in data.

• Points represent data values at specific times (e.g., months, years).
• Points are plotted on a grid with time on the horizontal axis (x-axis) and the quantity on the vertical axis (y-axis).
• Points are connected by straight lines to show how the data changes between recorded times.

Line charts help interpret whether values are increasing, decreasing, or staying constant over time.

For instance, if a shop records the number of customers each month, a line chart can show whether business is growing or declining.

Example: A shop records the number of customers over 5 months as follows:

• January: 120 customers
• February: 150 customers
• March: 130 customers
• April: 170 customers
• May: 160 customers

Plot these points on a graph with months on the x-axis and number of customers on the y-axis. Connect the points in order to see the trend.

You will notice an overall increase from January to April, then a slight decrease in May.

Bar Charts

Bar charts use rectangular bars to represent data. The length or height of each bar corresponds to the quantity it represents.

• Bars can be drawn vertically or horizontally.
• Each bar represents a category or group.
• The bars are spaced apart to show that categories are separate.
• The height or length of each bar is proportional to the value it represents.

Bar charts are useful for comparing quantities across different categories.

For example, a bar chart can show how many students prefer different types of fruit: apples, bananas, oranges, and grapes.

When drawing bar charts:

• Choose an appropriate scale on the value axis so bars fit well.
• Label each axis clearly, including units if applicable.
• Bars should be the same width and evenly spaced.

Example: The number of pets owned by children in a class is:

• Dogs: 8
• Cats: 5
• Rabbits: 3
• Fish: 6

Draw a vertical bar chart with pet types on the x-axis and number of pets on the y-axis. The bar for dogs will be the tallest at 8 units, cats shorter at 5, and so on.

Pictograms

Pictograms use pictures or symbols to represent data. Each picture stands for a fixed number of items.

• Symbols should be clear and easy to count.
• The key or legend shows how many items each symbol represents (e.g., 1 symbol = 5 cars).
• Partial symbols can be used to represent fractions of the unit.

Pictograms are visually appealing and make data easy to understand at a glance.

For example, if 1 smiley face represents 3 students, then 4 smiley faces represent 12 students.

When interpreting pictograms:

• Count the number of symbols for each category.
• Multiply by the value each symbol represents.
• Include partial symbols as fractions of the value.

Example: A pictogram shows the number of bicycles sold in a week. Each bicycle symbol represents 2 bikes. If there are 5 symbols for Monday, that means $5 \times 2 = 10$ bikes sold.