Final answer:
Concordance in twin studies is calculated as the number of concordant pairs divided by the total number of pairs.
Step-by-step explanation:
The correct formula for calculating concordance via twin studies is: Concordance = Number of concordant pairs / Total number of pairs. Concordance refers to the degree of similarity between twins in regard to a particular trait or condition. In twin studies, researchers compare the number of pairs where both twins have the trait or condition (concordant pairs) to the total number of pairs. For example, let's say there are 100 pairs of twins and 60 pairs have both twins exhibiting the trait or condition. The concordance would be calculated as: Concordance =
or 60%.