Data set:
Twins In a 1990 study by Suddath et al., reported in Ramsey and Schafer, researchers used magnetic resonance imaging to measure the volume of various regions of the brain for a sample of 15 mono-zygotic twins, where one twin was affected with schizophrenia and the other was unaffected. The twins were from North America and comprised eight male pairs, and seven female pairs ranging in age from 25 to 44 at the time of the study. The sizes in volume (cm3) of the hippocampus are in the file called Twins.
a. Should the data be analyzed as match pairs or be treated as if there were two independent samples?
b. Use appropriate graphics and summary statistics to describe the difference in brain volume for affected and unaffected twins.
c. Use the appropriate permutation test to ascertain if the difference in brain volume described in Part B is the result of schizophrenia or if it could be explained as a chance difference. Report your p-value and summarize your conclusion.