Negative relationship
In statistics, there is a negative relationship or inverse relationship between two variables, if higher values in one variable is associated with lower values in the other. A negative relationship between two variables usually implies that the correlation between them is negative, or—what is in some contexts equivalent— that the slope in a corresponding graph is negative. A negative correlation between variables is also called anticorrelation, or inverse correlation.
Example:
"They observed a negative relationship between illness and vaccination."
As incident of vaccination is increasing, incidence of illness is decreasing, and vice versa.
Compare to a positive relationship: Observed a positive relationship between illness and missed work.
As incidence of illness increased, sick days taken also increased.