An early hypothesis about schizophrenia (a form of severe mental illness) was that it has a simple genetic cause. In accordance with the theory, one-fourth (a 1:3 ratio) of the offspring of a selected group of parents would be expected to be diagnosed as schizophrenic.
Suppose that of 140 offspring, 19.3 percent were schizophrenic. Use this information to test the goodness of fit of a 1:3 model. Remember that a x2 analysis is performed on frequency counts.