Concerning polygenic traits it may be essential to be mindful of inter-genetic interactions or epistasis. Purging of deleterious mutations in sexual populations is facilitated by synergistic epistasis among deleterious mutations. Supplementary epistasis occurs when two loci affect the same phenotype. Bateson also coined the term "epistasis" to describe the genetic interaction of two independent loci. Positive epistasis between beneficial mutations generates greater improvements in function than expected. There is little statistical evidence for contributions from overdominance and epistasis. This relationship between number of mutations and fitness is known as "synergistic epistasis". The interplay among these genes is broadly used as an example of epistasis. This was the beginning of identifying gene interactions or epistasis. Negative epistasis and sex are thought to be intimately correlated. Numerous computational methods have been developed for the detection and characterization of epistasis. Terminology about epistasis can vary between scientific fields.