WJEC Maths for AS: Applied sample

2.2 Scatter diagrams and regression lines 27 2.2 Scatter diagrams and regression lines A scatter diagram is a visual representation of any relationship between two variables. Scatter diagrams are used to show possible relationships between bivariate data. Bivariate data is data that has pairs of values for two different variables. For example, you could collect pairs of values for shoe size and height to see if there is correlation between the two variables. Interpretation of correlation (positive, negative, zero, strong and weak) Correlation is a measure of how well two variables are related to each other. If when one variable increases, the other variable also increases this is called positive correlation. An example of this would be height and foot size – taller people generally take a greater shoe size. If an increase in one variable is associated with a decrease in the other this is called negative correlation. An example of this would be distance from the Equator and temperature. Generally, the further from the Equator, the lower the temperature. Positive correlation × × × × × × × × × × × × Negative correlation × × × × × × × If there is no relationship between the variables this is called zero correlation. For example there is no relationship between the height of a person and the number of pets owned, so this is zero correlation. Zero correlation × × × × × ×