Question: Suppose I have 100 monozygotic twin-pairs in which at least one of the twins has autism. Of these twin-pairs, 50 are concordant for autism and 50 are discordant.

1. Calculate the probandwise concordance and the pairwise concordance. (Show your calculation).

2. If both twins of a twin-pair are equally likely to be ascertained into my sample, which of these concordances should I calculate. Why?