Interpreting graphs
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Statistics
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Explainer Video
Summary
Interpreting graphs
In a nutshell
Graphs allow information to be displayed in a way such that it is easier to digest and understand. Coordinate grids with two axes, for example - and -axes, allow quick connections to be made between two sets of information. By using one coordinate, the other coordinate can be located by reading off the graph.
Coordinates reminder
When reading coordinates, you read the -coordinate first, then the -coordinate. The -coordinate shows how far left or right a point is and the -coordinate shows how far up or down a point is.
Example 1
has -coordinate and -coordinate .
The -coordinate is places to the right of the origin, as it is positive.
The -coordinate is places up from the origin, as it is positive.
Real-life graphs
Graphs are used to depict information, so are used in all sorts of real-life scenarios: for example tracking temperature against time, or distance against speed. Hence, being able to read a graph is crucial to their utility.
procedure
| 1. | Each point on a line or curve on a graph will have a pair of coordinates (usually and , but they can essentially be any letters). Locate the point you are interested in. |
| 2. | Read off its -coordinate (by looking at the horizontal axis and seeing which value on it the point is in-line with). |
3. | Read off its -coordinate (by looking at the vertical axis and seeing which value on it the point is in-line with). |
4. | You now have the coordinates of the point and can hence relate two pieces of information: the -value with the -value. |
Example 2
The graph below shows the relationship between time passed () and the temperature () of a cup of coffee in . What is the temperature of the coffee minutes after it is made?
Firstly, look along the time () axis (horizontally) at minutes.
Move up until you meet the line of the graph.
Finally, move across to read the temperature on the -axis.
FAQs - Frequently Asked Questions
What do coordinates on a graph mean?
If the point (x,y) is on a graph, it means that the x-value on the x-axis is related to the y-value on the y-axis.
Do graphs always use x and y?
Not all graphs use x and y. These are just conventions. Often more sensible letters will be used to make it clearer what they are representing, like in real-life graphs. Graphs do always have a horizontal axis and a vertical axis.
How do you read a graph?
Pick a point on a graph and see what point it is in-line with on the horizontal axis. This will be the x-coordinate. Then see what point on the vertical axis your point is in-line with. This will be the y-coordinate.