Definition
Negative association
Negative association means that larger values of one variable tend to go with smaller values of another.
What it means
Look at the pairs as a whole, not one point at a time. As you move right to larger x-values, the points generally move down to smaller y-values. A few points may break the pattern, because association describes an overall tendency.
Remember it
As one tends to climb, the other tends to fall.
Example
For a fixed 120 km journey, speeds of 40, 60, and 80 km/h give travel times of 3, 2, and 1.5 hours. The paired values move from larger time to smaller time as speed increases, so they show negative association.
Watch for
Negative association is a tendency across paired data, not a rule that every point must follow and not proof that one variable causes the other.
Common mix-up
Negative does not mean bad; it names the downward direction of the relationship.
Exact meaning
Two variables have negative association when, across paired observations, higher values of one generally occur with lower values of the other. On a standard scatter plot, the overall pattern tends to slope downward from left to right.