Which Graph Works Best
Analyse the effectiveness of different displays or visualisations in illustrating and comparing data distributions, then discuss the shape of distributions and the variation in the data.
Read this first
Different graphs show different things. Pick the one that answers your question.
A column graph makes it easy to see which is biggest.
Words you need
- Compare
- Look at two things side by side.
- Spread
- How far apart the results are.
- Shape
- What the data looks like as a whole.
Worked example
e.g. Which display shows the most popular colour fastest?
- Look at a list of names. You have to read every one.
- Look at a column graph. The tallest bar jumps out.
- The graph answers it in one look.
- A column graph is best for comparing groups.
Ask what your question is. Then pick the display that answers it.
Practice
The pictures fade as you go. By the last few you are on your own.
1Which colour is least popular?with a picture
AnswerGreen. Its column is shortest.
2Are red and blue close or far apart?with a picture
AnswerClose. Only 2 apart.
3Would a pictograph or a list be faster to read?with a hint
Need a hint?
Which one can you see at a glance?
AnswerThe pictograph.
4One column is much taller than the rest. What does that tell you?with a hint
Need a hint?
Think about how spread out the data is.
AnswerOne answer was far more popular.
5Why not use a graph for only two numbers?on your own
AnswerYou can just compare them. A graph adds nothing.
6A graph has no labels. What is wrong with it?on your own
AnswerYou cannot tell what it shows.
7Name one thing every graph needs.on your own
AnswerA title, labels and a scale.
Think about it
1
Can two graphs of the same data look different?
One good answerYes. Changing the scale changes how big the gaps look.
2
What makes a graph easy to read?
One good answerClear labels, a title and a scale starting at zero.
Common mistakes
Thinking a taller bar always means a lot more.
Check the scale first.
Leaving off the labels.
Then nobody knows what the graph is about.