Drawing a bar chart

A bar chart shows how much there is of each thing — using bars of different heights.

count
  6 |                 █
  5 |     █           █
  4 |     █           █
  3 |     █     █     █
  2 |     █     █     █
  1 |     █     █     █
  0 +-----------------------
      dog   cat   fish

How to read it: find the bar, follow it upwards, and see which number it reaches. Cat reaches 3. Fish reaches 6.

Three things a good chart must have:

1. What the bars show — a name under each bar.
2. Numbers up the side — otherwise you cannot tell how much.
3. A title — what is the chart about?

One important rule: bar charts should start at zero. If they start at 2, a bar of 3 looks half the size of a bar of 4, even though the difference is only one.

Make your own bar chart. You need squared paper and a pencil.

Step 1 — collect. Ask ten people about something with a few answer options:

• Which pet do you like best? (dog / cat / fish / other)
• Which season do you like best?
• How do you get to school? (walk / cycle / bus / car)

Make a tally mark for each answer.

Step 2 — count. Count the tally marks for each option.

Step 3 — draw.

• Draw one line going down (the numbers) and one going right (the options).
• Write 0, 1, 2, 3 … along the downward line.
• Draw a bar for each option, all the same width, with gaps between them.
• Write the names under the bars.
• Write a title at the top.

Step 4 — read your own chart.

• Which option got the most?
• How many more did it get than the smallest?
• If you asked ten more people — do you think it would come out the same?

That last question is the most important one. Ten people is not very many. Ask ten more and the answer could be different — especially if you ask completely different people.