Bar Graphs
4.0 Data Handling · 4.1 Bar Graphs
Syllabus tag: Kenya CBC | Grade 6 Mathematics | Strand 4.0 Data Handling | Sub-Strand 4.1 Bar Graphs (10 Lessons)
Lesson objectives
By the end of this topic, you will be able to:
- Draw a frequency table from real-life data
- Represent data using pictographs
- Represent data using bar graphs
- Interpret information from bar graphs
- Appreciate the use of bar graphs in real life
Bar Graphs
Numbers in a list are hard to compare. Drawn as bars, the answer is clear at a glance.
a) Collecting data
Data is information you collect to answer a question.
Ask a clear question first. "Which game do learners like best?" is a good one.
Then ask everyone and record the answers as you go.
b) A frequency table
A frequency table shows how many times each answer came up.
| Game | Tally | Frequency |
|---|---|---|
| Football | IIII IIII IIII | 14 |
| Netball | IIII IIII | 10 |
| Running | IIII I | 6 |
| Chess | IIII | 4 |
Make tally marks in groups of five, with the fifth crossing the other four. Counting in fives is quick and you make fewer mistakes.
Frequency just means how many.
Add the frequency column at the end. It should match the number of people you asked. Here it is 34.
c) Pictographs
A pictograph uses a small picture to stand for a number of things.
The key tells you what one picture is worth. If one picture stands for 2 learners, then 7 pictures mean 14 learners.
Half a picture means half the key value.
Pictographs look friendly but are awkward when the numbers do not divide neatly.
d) Bar graphs
A bar graph shows each group as a bar. The taller the bar, the bigger the number.
Leave a gap between the bars, because the groups are separate things.
Make all the bars the same width. Only the height should change.
e) Drawing one properly
Start the number line at zero. Starting higher makes small differences look huge.
Choose a scale that fits your paper and is easy to read. Counting in 1s, 2s, 5s or 10s is sensible.
Label both sides. Write what the bars show along the bottom, and what the numbers mean up the side.
Give it a title so a reader knows what it is about.
f) Reading a bar graph
Find the tallest bar for the most popular, and the shortest for the least.
To read a value, follow the top of the bar across to the number line.
To compare two bars, subtract the smaller from the larger.
g) Where this is used
A school shows attendance. A shop tracks what sells. A newspaper turns a survey into a picture. A health centre counts visits each month.
Words to know
- Frequency table — a table listing each category with a count of how often it occurs.
- Pictograph — a chart using repeated pictures or symbols to represent quantities.
- Bar graph — a chart using bars of different heights to represent and compare quantities.
- Frequency — how many times something occurs.
:::checkpoint Check yourself
- What does frequency mean?
- Why should a bar graph start at zero?
- In a pictograph, what does the key tell you?
- Why are gaps left between bars? :::
Bridge to practice
Try the exercises below — reading values from the bar graph, and working out totals and differences from it.