By comparing monozygotic and dizygotic twins, scientists have determine that about 50% of the variation differences in “religiosity” within white, middle-class Americans is due to genetic difference. Religiosity refers to the strength of religious belief, not church membership or attendance. It is measured using a questionnaire.

(a) Explain what this means.

(b) Suppose that average measured religiosity is lower in Denmark than in the US. Does this mean that 50% of the difference between Danes and Americans is genetic? Explain.