Line Graphs Over Time
Interpret line graphs representing change over time; discuss the relationships that are represented and conclusions that can be made.
Read this first
A line graph shows how something changes over time. The slope tells the story.
The line goes up, so the temperature is rising.
Words you need
- Line graph
- A graph that joins points to show change.
- Trend
- The general direction the line goes.
- Interval
- The gap between marks on the scale.
Worked example
e.g. A line graph shows temperature through the day. What does a rising line mean?
- Read the bottom axis. It shows the time.
- Read the side axis. It shows the temperature.
- Follow the line from left to right. It goes up.
- A rising line means the temperature is going up.
Read both axes before you read the line. Otherwise the shape means nothing.
Practice
The pictures fade as you go. By the last few you are on your own.
1Is the temperature rising or falling?with a picture
AnswerFalling. The line goes down.
2What does a flat line mean?with a picture
AnswerNo change. It stayed the same.
3A steep line and a gentle line both rise. What is different?with a hint
Need a hint?
Think about how fast.
AnswerThe steep one is changing faster.
4Why join the points on a line graph?with a hint
Need a hint?
What happens between the readings?
AnswerTo show the change between them.
5Would a line graph suit favourite colours?on your own
AnswerNo. Colours do not change over time.
6What must every axis have?on your own
AnswerA label and a scale.
7A line goes up then down. Describe it.on your own
AnswerIt rose, then it fell.
Think about it
1
When is a line graph better than a column graph?
One good answerWhen the data changes over time.
2
What does the steepness of a line tell you?
One good answerHow fast the change is happening.
Common mistakes
Joining points for data that is not over time.
Line graphs are for change, not categories.
Ignoring the scale.
A small change can look huge if the scale is stretched.