Correlation

A scatter diagram (or scatter graph) is a type of graph used to display paired data. Each point on the graph represents one pair of values, such as height and weight. Scatter graphs help identify patterns and relationships between two variables.

How to Draw a Scatter Graph

1. Label the axes:
   • The independent variable (the one you control or choose, such as time) goes on the horizontal axis ($x$-axis).
   • The dependent variable (the one you measure, such as distance) goes on the vertical axis ($y$-axis).
2. Choose a suitable scale for both axes to fit the data.
3. Plot each pair of values as a single point on the graph.

Describing Correlation

Correlation describes the relationship between the two variables. Look at the pattern formed by the points:

• Positive Correlation: The points slope upwards from left to right. As $x$ increases, $y$ increases.
• Negative Correlation: The points slope downwards from left to right. As $x$ increases, $y$ decreases.
• No Correlation: The points are scattered randomly, with no clear pattern.

Strength of Correlation

• If the points lie close to a straight line, the correlation is strong.
• If the points are more spread out, the correlation is weak.

Interpreting Scatter Graphs

When interpreting the correlation you will need to state:

"As the independent variable increases, the dependent variable increase/decreases."

If the correlation is positive, the word will be increases, if it is negative the word will be decreases.