If two different measures are closely related, they produce a high positive correlation. For example, intelligence test scores and reading skills often show a high positive correlation. There are many measures which tend to vary together. The scatter plot of such a relationship would be indicative of a low positive correlation. Figure 5-C shows the distribution of heights and weights that may be found in a typical college classroom 4 .
Most measures are totally unrelated.
In a correlation of height and hair color, the points of the scatter plot would be random and no trend could be obtained in any direction. Figure D shows a zero correlation. The negative correlations are interpreted in exactly the same way as the positive correlations but the relationships are in the reverse direction. That is, higher scores on one measure tend to be associated with low scores on a second measure. An example of a highly negative correlation may be the age of an automobile and its selling price.