Are Severe Psychiatric Disorders Related to Biological Factors? One study used x-ray computed tomography (CT) to collect data on brain volumes for a group of patients with obsessive-compulsive disorders and a control group of healthy persons.

The accompanying list shows sample results (in milliliters) for volumes of the right cordate (based on data from “Neuroanatomical Abnormalities in Obsessive-Compulsive Disorder Detected with Quantitative X-Ray Computed Tomography,” by Luxenberg et al., American Journal of Psychiatry, Vol. 145, No. 9). Use a 0.01 significance level to test the claim that obsessive-compulsive patients and healthy persons have the same brain volumes. Based on this result, can we conclude that obsessive-compulsive disorders have a biological basis?