Scatter Graphs and Correlation

Plotting two quantities together

• A scatter diagram plots pairs of measurements taken from the same thing, one quantity on each axis
• Each item of data gives one point, so twelve people measured for two things gives twelve points
• The syllabus asks for points to be clearly marked, for example as small crosses, and they are never joined up
• Questions frequently give a diagram with most points already plotted and ask you to add the last few
• Read the scale on both axes before plotting, since the two axes rarely use the same one