Line Charts, Bar Charts & Pictograms

What Is a Line Chart?

A line chart (sometimes called a vertical line graph) is a visual way to show how often each value occurs in discrete numerical data.

The x-axis shows the values (e.g. test scores, number of pets).

The y-axis shows the frequency (how many times each value occurs).

Each data point is represented by a vertical line—the taller the line, the more frequent the value.

Example:

The table below shows how many students got each score in a quick quiz:

A line chart shows tall lines at 5 and 6, with the tallest at 5 (7 students got it).

So, the mode (most common score) is 5.

What Is a Bar Chart?

A bar chart is used for discrete or categorical data.

Categories or values go on the x-axis.

Frequency goes on the y-axis.

Each bar's height = frequency.

Bars are separated by small gaps (unlike histograms).

Example:

This bar chart shows students’ favourite ice cream flavours:

The highest bar is Chocolate, so it's the most popular flavour.

Dual Bar Charts

These show two sets of data side by side—useful for comparing!

Each month would have two bars, one for each year group.

What Is a Pictogram?

A pictogram uses pictures or symbols to show frequency.

There are no axes—just rows of icons

You’ll be given a key that says what each symbol is worth. Sometimes, half or quarter symbols are used.

Example:

The pictogram below shows how many students walk to school:

Worked Example

Miss Patel asked her Year 9 and Year 10 students how many pets they have. She created a dual bar chart to show the results.

(a) What is the modal number of pets for Year 9?

Mode = Most common number

The tallest Year 9 bar is at 1 pet

Answer: 1

(b) How many Year 10 students were asked?

Add up the Year 10 frequencies:

4 + 6 + 5 + 3 = 18 students

 
Key Takeaways

• Line charts = best for scores, marks, or anything counted.
• Bar charts = great for showing categories or comparisons.
• Pictograms = fun and visual, but watch the key