Interpreting graphs

Interpreting graphs

The gradient of a straight line of best fit can give information about the relationship between two variables in a graph.
To calculate the gradient, choose two points on the lines as far apart as possible such that their x and y values are easy to read and calculate the differences in the two x and the two y values. The gradient will be difference in y ÷ difference in x.
A curved line of best fit has a changing gradient. The gradient at a particular point can be calculated by drawing a tangent.
- A tangent is a straight line that only just brushes against the point on the curve.
- The gradient of the curve is the gradient of this straight-line tangent.
The x or y intercept is the point where the line crosses the x or y axis.
The area under a line graph is the value that corresponds to multiplying together the two variables shown in the graph as they are both changing.
- For straight line graphs, this area can be calculated using the formula for the area of a rectangle or a triangle.
- For curves, this area can be estimated by counting the squares beneath the graph.

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