EDEXCEL GCSE FOUNDATION MATHS - What are Scatter Graphs

Edexcel GCSE Foundation Maths - What are Scatter Graphs?

Scatter graphs are a type of graph used to show the relationship between two sets of data. They are particularly useful for exploring whether there is a correlation between the two variables.

Understanding the Basics

• Axes: Scatter graphs have two axes, typically labeled with the names of the variables being investigated. The horizontal axis is called the x-axis, and the vertical axis is called the y-axis.
• Data Points: Each point on the scatter graph represents a pair of data values. The x-coordinate of the point corresponds to the value of the first variable, and the y-coordinate corresponds to the value of the second variable.

Interpreting a Scatter Graph

Once you have a scatter graph, you can analyze the relationship between the variables by looking for patterns in the data points.

• Positive Correlation: If the data points tend to rise from left to right, the variables have a positive correlation. This means that as the value of one variable increases, the value of the other variable also tends to increase.
• Negative Correlation: If the data points tend to fall from left to right, the variables have a negative correlation. This means that as the value of one variable increases, the value of the other variable tends to decrease.
• No Correlation: If the data points are scattered randomly, there is no correlation between the variables. This means that there is no clear relationship between the two variables.

Example:

Imagine we are looking at the relationship between the number of hours studied and the exam score.

• x-axis: Number of hours studied
• y-axis: Exam score

If the scatter graph shows a positive correlation, it suggests that studying more hours leads to higher exam scores. If it shows a negative correlation, it suggests that studying more hours leads to lower exam scores (unlikely in this case!). No correlation would mean that there is no connection between the number of hours studied and exam score.

Key Points:

• Scatter graphs are used to explore relationships between two variables.
• They can show positive, negative, or no correlation.
• The direction of the points on the graph indicates the type of correlation.

Practice:

Look at the scatter graph below. What type of correlation is shown?

[Insert a sample scatter graph showing a positive correlation]

This graph shows a positive correlation between the two variables. As the value of the variable on the x-axis increases, the value of the variable on the y-axis also tends to increase.