Ah, this one. Say you have a sample group with the size of 10000 people (all randomly picked). The prevalence of autism is calculated to be around 1% of an typi

Ah, this one. Say you have a sample group with the size of 10000 people (all randomly picked). The prevalence of autism is calculated to be around 1% of an typical population. This would mean that the group consists of about 100 people who are autistic. The accuracy of this test is 90%, and thus this would yield a positive result of about 90 people who really have autism, and about 1000 people who don't.